I've wanted something that merges the 3D martial arts combat of Bungie's old game Oni with the freerunning environmental exploration of Mirror's Edg3.
Bonus points for multiplayer mode, hand-to-hand weapons, and just a little more granularity in the hand-to-hand combat engine (when Barrabas would hold you up in the air dangling for a full second before uppercutting you into the stratosphere, it always seemed like you should have been able to kick him in the face). Decent enemy AI would be important (Oni's was not especially good).
Bonus points for multiplayer mode, hand-to-hand weapons, and just a little more granularity in the hand-to-hand combat engine (when Barrabas would hold you up in the air dangling for a full second before uppercutting you into the stratosphere, it always seemed like you should have been able to kick him in the face). Decent enemy AI would be important (Oni's was not especially good).