Gotta go with Perspective (it's free, btw) - it's a 2D platformer" with a 3D perspective, but not in the way you'd think.

Essentially, you have 2 modes: first-person walking/camera adjusting and 2d platforming. The first-person mode allows you to align the platforms to helpful positions from the perspective, and then swap mode to 2d platformer to walk on those platforms. Part of the trick is that the 2d guy stays the same size on your screen, but you must adjust the perspective so he can fit through gaps and such. You switch back and forth to help the platformer guy through levels.

Definitely for fans of Portal, Superliminal and the likes. No real story in this one though, but gameplay is kinda-ish similar.