I think I might also propose that we alter the Ninja Easter egg one to be any Easter egg. I just think the ninja thing is too specific. Nobody has ever gotten it, and I can't imagine it happening any time soon. But that means it needs another good creative name. Thoughts?

Accomplishments:

Leveled Up: You learned something that you didn't know that you can reuse in other games or other programs.
Mission Accomplished!: The challenge ends, and you actually have a game to show for it!
Better Late Than Never: Complete your game after the competition has ended by less than a month.
You're Still Working on That?: Complete your game after the competition has ended by more than a month.
The Great Unveiling: Provide a download for your game.
Victory: Beat your game for the first time!

Phailures:

Wait, We Were Supposed to Make a Game?: The challenge ends, and you don't get the Mission Accomplished! achievement.
"Research": You spend a few hours playing a game when you should have been making one.
Gratuitous Blood: Your explosions and deaths result in far more destruction than is necessary or even believable.
Happy Accident: You accidentally create a bug that leads to humorous results. Post the video or screenshot in the Happy Accident thread.
Back of the Line: Don't get started until the competition is well underway.
Monday: The entire weekend went by and you didn't get any programming done.
That's Quite a Bite: Eliminate at least one game feature due to time pressure or lack of programming knowledge.

Artwork/Sound:

It's Just Temporary: You put in artwork in your game that you claim is temporary, until you or your friend can provide you with better art.
The Apprentice Becomes the Master: The competition ends and your temporary art becomes permanent without ever being upgraded to the final version, which was never made. (Requires: "It's Just Temporary")
8 is Enough: Use old school 8 bit graphics or sound/music in your work. Could also be a midi file on the music side.
Vincent van Gogh: You create your own artwork for your project.
I'm a Lover, Not an Artist!: You get all, or most of your work, from online sources and do very little of your own artwork.
Silence is Not Golden: Add sound effects or background music to your game. 8 is Enough optional.

Features:

Game Over: You implement the ability for players to lose the game. (Also, you just lost the game.)
Ninja's Don't Take Off Holidays: Created an Easter Egg featuring a ninja.
Konamified: Make the Konami Code do something interesting in your game.
Prototype: You have something that could loosely be called a working game by the end of the first weekend.
What, Writing? We're Talking About a Video Game: Create a story (however simple) and implement it into your game.
Additions: Add at least one game feature that you weren't planning on or didn't think you had time for.
Two Can Play This Game!: You make your game multiplayer (same computer/device, LAN, or Internet all count).
I'm Sorry, Dave. I'm Afraid I Can't Do That.: Add an AI enemy, opponent, or component to your game. It doesn't have to be any good.

Actual Coding:

Law of Live Demos: You show your WIP to somebody. Something goes horribly wrong.
Time Machine: Worked for over an hour on code that you rip out later that day.
The Thinker: Spend a hour thinking through a complicated piece of code and get it right first try.
The Tinker: Fiddle with a complicated piece of code and get it to work only after a lot of failed tweaks.
Head Banger: Use recursion in some form in one of your games.
Occam's Razor: Simplify overly complex code into something smaller and more efficient (The simplest explanation is usually the best)
You've got Class, Baby!: Comment all your classes so they are easy for others to reuse and understand. Since this one may go on forever depending on your number of classes, to earn the badge, you should hit a minimum of 25 commented classes.
That's a Lot of Text!: Comment every line of code in your project to spell things out clearly.
Applying Research: Spend at least an hour programming when you should be doing something else.
Jurassic Programming: While making your game run into a situation where you must add a ton of code lines to get something to work. (IE: adding points into a collision detection array) - "I wrote a million lines of code to run this park!"
Less is More: Lines of code ain't everything. Sometimes, the best solution is to refactor to eliminate redundant lines of code, leaving you with less but better designed code. Do this and unlock this achievement.
Lonely: Program on a Friday or Saturday evening.

Miscellaneous:

You Got Tropes: Use at least three tropes of the game chosen as the theme.
Moral Support: Leave a comment on somebody else's game thread with (constructive) feedback.
The Buddy System: Spend all or part of the challenge building a game in a team.
Change Of Plans: You stop making the game you originally entered and instead enter a new one. Whether you got bored, stuck, or whatever, the whole point is to have fun and make something you like!
Way to Brag: Claim at least 15 achievements
Special Thanks: Create a credits screen which list all those who have contributed to your project.
Thinking Ahead: Spend time before the start of the competition planning your game.
Joined The Rebels: Officially Proclaim yourself a Rebel in this competition.

Time/Loc:

3 AM Code Fest: You spend several hours programming your game between the hours of midnight and 6 AM. Beer and pizza optional.
10 Hours: You spend at least 10 hours programming your game during the month.
25 Hours: You spend at least 25 hours programming your game during the month.
50 Hours: You spend at least 50 hours programming your game during the month.
100 Hours: You spend at least 100 hours programming your game during the month.
½KLOC: Your game reaches 500 lines of code. You're off to a great start!
1KLOC: Your game reaches 1000 lines of source code. Making progress! Excellent!
2KLOC: Your game reaches 2000 lines of source code. Keep it up!
3KLOC: Your game reaches 3000 lines of source code. Your game definitely has some weight behind it!
5KLOC: Your game reaches 5000 lines of source code. Well done!
10KLOC: Your game reaches 10000 lines of code. That is a lot of zeroes! And it's 16 in binary! (That makes it sound… rather unimpressive!)
15KLOC: Your game reaches 15000 lines of source code. Are you programming in your sleep or something?
20KLOC: Your game reaches 20000 lines of source code. Are you just copying and pasting lines of code to unlock achievements?
25KLOC: Your game reaches 25000 lines of source code. OK, you must be cheating. How are you writing this much code?

Also:
Thinking Ahead: Spend time before the start of the competition planning your game.

These achievements are self-claimed. When you feel like you've met the criteria for the achievement, then claim it as your own accomplishment! (Most people list their achievements in their game's development thread, but it's not required.)

This list is not exhaustive. If you feel like you've done something that deserves recognition (or a self-deprecating dubious award about new creative ways you wasted time) add a new post with the achievement so everybody else can claim it too!

It's Just Temporary: You put in artwork in your game that you claim is temporary, until you or your friend can provide you with better art.

The Apprentice Becomes the Master: The competition ends and your temporary art becomes permanent without ever being upgraded to the final version, which was never made. (Requires: "It's Just Temporary")

Law of Live Demos: You show your WIP to somebody. Something goes horribly wrong.

Game Over: You implement the ability for players to lose the game. (Also, you just lost the game.)

Gratuitous Blood: Your explosions and deaths result in far more destruction than is necessary or even believable.

Happy Accident: You accidentally create a bug that leads to humorous results. Post the video or screenshot in the Happy Accident thread.

Time Machine: Worked for over an hour on code that you rip out later that day.

Ninja's Don't Take Off Holidays: Created an Easter Egg featuring a ninja.

Konamified: Make the Konami Code do something interesting in your game.

Head Banger: Use recursion in some form in one of your games.

8 is Enough: Use old school 8 bit graphics or sound/music in your work. Could also be a midi file on the music side.

Occam's Razor: Simplify overly complex code into something smaller and more efficient (The simplest explanation is usually the best)

You've got Class, Baby!: Comment all your classes so they are easy for others to reuse and understand. Since this one may go on forever depending on your number of classes, to earn the badge, you should hit a minimum of 25 commented classes.

That's a Lot of Text!: Comment every line of code in your project to spell things out clearly.

Vincent van Gogh: You create your own artwork for your project.

I'm a Lover, Not an Artist!: You get all, or most of your work, from online sources and do very little of your own artwork.

Special Thanks: Create a credits screen which list all those who have contributed to your project.

"Research": You spend a few hours playing a game when you should have been making one.

10 Hours: You spend at least 10 hours programming your game during the month.

25 Hours: You spend at least 25 hours programming your game during the month.

50 Hours: You spend at least 50 hours programming your game during the month.

100 Hours: You spend at least 100 hours programming your game during the month.

Moral Support: Leave a comment on somebody else's game thread with (constructive) feedback.

Leveled Up: You learned something that you didn't know that you can reuse in other games or other programs.

3 AM Code Fest: You spend several hours programming your game between the hours of midnight and 6 AM. Beer and pizza optional.

Prototype: You have something that could loosely be called a working game by the end of the first weekend.

Back of the Line: Don't get started until the competition is well underway.

The Thinker: Spend a hour thinking through a complicated piece of code and get it right first try.

The Tinker: Fiddle with a complicated piece of code and get it to work only after a lot of failed tweaks.

You Got Tropes: Use at least three tropes of the game chosen as the theme.

What, Writing? We're Talking About a Video Game: Create a story (however simple) and implement it into your game.

Way to Brag: Claim at least 15 achievements.

Monday: The entire weekend went by and you didn't get any programming done.

Victory: Beat your game for the first time!

The Buddy System: Spend all or part of the challenge building a game in a team.

Mission Accomplished!: The challenge ends, and you actually have a game to show for it!

Wait, We Were Supposed to Make a Game?: The challenge ends, and you don't get the Mission Accomplished! achievement.

½KLOC: Your game reaches 500 lines of code. You're off to a great start!

1KLOC: Your game reaches 1000 lines of source code. Making progress! Excellent!

2KLOC: Your game reaches 2000 lines of source code. Keep it up!

3KLOC: Your game reaches 3000 lines of source code. Your game definitely has some weight behind it!

5KLOC: Your game reaches 5000 lines of source code. Well done!

10KLOC: Your game reaches 10000 lines of code. That is a lot of zeroes! And it's 16 in binary! (That makes it sound… rather unimpressive!)

15KLOC: Your game reaches 15000 lines of source code. Are you programming in your sleep or something?

20KLOC: Your game reaches 20000 lines of source code. Are you just copying and pasting lines of code to unlock achievements?

25KLOC: Your game reaches 25000 lines of source code. OK, you must be cheating. How are you writing this much code?

Better Late Than Never: Complete your game after the competition has ended by less than a month.

You're Still Working on That?: Complete your game after the competition has ended by more than a month.

Silence is Not Golden: Add sound effects or background music to your game. 8 is Enough optional.

The Great Unveiling: Provide a download for your game.

Applying Research: Spend at least an hour programming when you should be doing something else.

That's Quite a Bite: Eliminate at least one game feature due to time pressure or lack of programming knowledge.

Additions: Add at least one game feature that you weren't planning on or didn't think you had time for.

Jurassic Programming - While making your game run into a situation where you must add a ton of code lines to get something to work. (IE: adding points into a collision detection array) - "I wrote a million lines of code to run this park!"

Less is More: Lines of code ain't everything. Sometimes, the best solution is to refactor to eliminate redundant lines of code, leaving you with less but better designed code. Do this and unlock this achievement.

Lonely: Program on a Friday or Saturday evening.

Change Of Plans: You stop making the game you originally entered and instead enter a new one. Whether you got bored, stuck, or whatever, the whole point is to have fun and make something you like!

Two Can Play This Game! You make your game multiplayer (same computer/device, LAN, or Internet all count).

I'm Sorry, Dave. I'm Afraid I Can't Do That. Add an AI enemy, opponent, or component to your game. It doesn't have to be any good.

Thinking Ahead: Spend time before the start of the competition planning your game.

Heads Up: Add a Head-up Display or other UI overlay to your game.

Widget Factory: Add a UI of some sort to your game, with buttons, sliders, check boxes, etc.

Seeing the Matrix: Share your source code with the people in the competition via GitHub, BitBucket, or a simple download.