Some ideas may not make sense:
Chainsaw hand.
Hyper-jump (movement enhancement).
Turbo-boost (run speed enhancement).
Implanted Firearm.
Implanted Grenade Launcher.
Water Resevoir.
Implanted Wet Bar. Like Water Resevoir, but for booze.
Hydro-electric Power Source. Uses filtered (clean water) to recharge power batteries.
Emotional Inhibitor. Ignores morale effects while powered. With some sort of negative side-effect perhaps?
Holographic Decoy. Effect on monsters similar to noise emitter, but visual only.
Scent Decoy. As above, but scent only.
Monofilament Whip. Very high cutting damage, very fragile.