Sometimes i imagine my environment as an FPS, but realistically done via the Crytek or U3 engine. Usually i think of how i'd do a remake of an old game in First Person, like Outcast, Omikron, Flashback. How i would do away with the Crouch/jump buttons and make them more automatic....like auto leap over a fence complete with proper head tilts, ducking under things..stuff that we do automatically in real life without much thought. Like walking through the woods, your head sways and tilts around branches constantly. just more realistic movements that are more animated, although it would make some sea sick.
I also like to think of all the cool stuff from various FPS games and put them in one..like mixing the jumps and other movements of Mirrors edge, the pulling out bullets from your leg and run slide in Farcry 2, the RPG like parts of Stalker..etc. in enviros were you can ride vehicles/fly dragons depending on type of game. Seems most fpst games feel very static in how you move and FC2 and Mirrors Edge would make a great combo for any FPS.