After playing a ton of SF4 just now, I had an idea for a game! It would be a first person version of street fighter, either with more realistic guns (i play as dhalsim ;p ), or with neat special moves, or maybe even some sort of upgrading move/weapon system, although the key of the game would be 1v1 on a smaller map with short times between the rounds and a good matchmaking system, sort of like sf4's 1v1 battles with short loads between rounds. Except in first person, probably with guns, and either in realistic mode like a modern warfare 2 1v1 mod with player rankings, possibly a subgame type in a fps like mw2, or alternatively a more cartoony version where players can take more damage and the weapons are a bit more spectacular, although probably with an emphasis on ranged combat over melee due to the first person perspective.

That being said, doing some sort of first person brawling/melee game might also be neat. One way to do it would be to have the sf4 source code and play normally with the camera fixed inside one of the characters heads, and go from there? Although making a first person brawling system does sound kind of tricky...ranged attacks seem to be a bit simpler in a lot of ways, although in first person it might be good to have the mouse look around as per a normal first person, with each mouse button controlling one arm, so left button is left arm, then there's a crosshair on the middle of the screen, and whatever body location is targetted is highlighted, so if it's centered on your opponent's head, cheek, eye, left hand, etc, that part lights up, and clicking the mouse attempts to move that limb to the highlighted location, which could be a moving location such as your opponent's hand for a block, and clicking while holding a weapon would attempt to fire the weapon at the highlighted target near the center of the screen. Click their head to punch or attack with a melee weapon, two handed weapons would just use one button, and foot movement could still be controlled with wasd in a traditional manner.