Start rumors. Say people said things that they didn't. Use their corpses as platforms. This is what a "Mean Girls" game should've been.
Fib is a pretty coolass pants twist on the "manipulate NPCs" sub-genre of platformers, the theme for Ludum Dare 18. Ideas like this are especially great because they're (a) simple, (b) intuitive, (c) funny, (d) only work in platformers. I don't think this type of thing would work too well in an FPS setting without a lot of changes.