I guess we need to figure out what we're doing fairly quickly now, but I wanted to throw in a few additional ideas besides the ones we've got. (Not that we necessarily need more ideas. I like the ones that have been brought up so far.)
We've done three collabs so far: Blockade, RoboTron, and Xevious. We could take any of those and make it 3D. We could possibly build on the same codebase, but I think I'd personally vote against that. This idea might have more allure if we have the same team of people who made one of those, and I don't think there's a guarantee of that. But Blockade would be pretty dang easy in 3D, since it's just blocks. Xevious wouldn't be crazy difficult either, though the 3D modeling might be a bit more complicated. (Honestly, probably not that bad. I think I could put together the 3D models we used in the last collab within about an hour.)
The Asteroids that Brett208 mentioned would fit into this category as well, and I think that would be very doable.
Here's my other idea.
So before we did any of these collabs, my and some friends in college did things very much like this. (That's what inspired these collabs.) It was 8 hours on a Saturday. I put together a video of the different games we made, and two stick in my head the most.
The first was a generic tank game. You can see it here in the demo video. The game used gamepads (which work on a PC). One thumbstick controlled movement, the other controlled where you were aiming. A to shoot. The game mechanics were pretty simple. The 3D modeling took a bit of time, but I'm sure we could find some stuff and/or go with really simple models. We didn't quite get there when my friends did it, but this game could also include AI, if somebody wanted to tackle that. The game world was 3D visually, but from an AI perspective, it was basically a 3D world.
The second was a generic space shooter. You can see that in the demo video as well. I spent the first 3 or 4 hours trying to get movement to work out right with yaw, pitch, and roll before abandoning it in favor of quaternions. That's about as crazy as the 3D world gets (well, particle effects can also get a little tricky) and I'd be happy to volunteer to do that so others don't have to.
Both of those two games are quite a bit more involved than I think most people were expecting, but I think we as a collective are better at making games than my friends and I were 7 years ago. It would be a challenge, for sure, but I'm confident we could do it. And I'd love a second shot at those two games.
So there. About 5 more game ideas to consider.
If anybody else has other ideas that they want to throw in for consideration, now's the time to do it.
Let's cut off game suggestions 24 hours from now, and then vote in the day or so after that. How's that sound?