How about a weapon (maybe a syringe launcher or something) that, when it kills someone, replaces them with an identical bot (basically, them, with all their weapons, but only 25% health) that you can control? The gun wouldn't do much damage except on headshots, which would kill in two hits or so. That means you could kill some guy with a machine gun and use his firepower to your advantage. However you'd be motionless and completely vulnerable while controlling them, so it'd be risky unless you had a good hiding spot.
Also you could infiltrate their base, but to balance it maybe there should be a limit on the length of time you could control a body, or something to make it possible to notice that "teh_pwnz0r" was taken over, but not obvious?
Poll