I happen to have a few ideas...
1. When you look dow you see your legs, and they can cause ripples in water, like in Halo 3
2. Blowing off body parts, like in FEAR, Unreal Tournament 3, Gears of War, FEAR Exraction Point, and Timeshift.
3. Okay, this may sound way to advanced, but with some insane scripting skils it is possible; when you are near something you can go into cover with, you click a button, like C for cover, and you slide into the wall, going into 3rd person view, like in Rainbow Six: Vegas
4.Maybe Something like WoW character viewier, or Forge, so you can click and make people move, and control the camera in game, making cutscenes much easier to do.
5. Vehicles, such as the Humve, and when you go near it, press e, or enter to go inside and drive it.
6. Turrets, go near it and press e or enter to use it
7. Something like a "Slow-mo" mode like in fear, so you can easily survive complex battls, all this would make for some seriously intense battles.
I know that most of these are increasly hard to script, as I have tried myself, failing at every attempt lol. But I beleive that Lee and other hard-core coders would have a better chance at all this..
If you wish to help me on my upcoming game, then you may send me an e-mail at vincentcody@hotmail.com, you will be responded to in less than 3 days...