Title: ZXWQZX (possibly short for "I'll rename this later")
Players: 2, coop
Controls: Controller strongly
Concept: Super Meat Boy meets the coop nature of Monaco and Portal 2.
Technology: codeheart.js + gamepad extensions, svn, Photoshop, emacs, whatever tools I find that have value
Basically, first take all of the awesome components of Super Meat Boy: very short (usually <20s if played perfectly) but brutally difficult levels, very tight controls, easy to die and easy to try again, visual cues to help you see where you've failed before. Then, throw in slick co-op ala Monaco (for a recent indie 2d-game example) or Portal 2 (for the 2-player nature).
Integrating controller support.
Implementing the base one-person mechanics.
Implementing co-op mechanics that are essential but do not break the game.
Making a good enough level editor to bang out a few levels without going insane.
Making a slick camera system that allows players to be far away from each other without either person being off-screen and without zooming out too far.
I'll be doing the hardcore track, since I have family and friend stuff this weekend and the 4th of July. And I'm young and naive enough to think its a good idea to work 48 hours straight.