ZED gun (original, not MKII):
motion sensor, high ammo pool, and damage amp alt fire makes it a great off-perk weapon for any perk to pick up on the side.
Bionic energy gloves for Martial Artist as a tier 4:
punching zeds with metal energy gloves sounds awesome and they'd have some neat and useful mechanics. Normal punches just do damage. Heavy punches are a low energy cost large radius explosion that do more damage than the normal punch, but only damage the target hit; the explosion stumbles all zeds in a radius around the punched zed. Holding alt-fire would charge up energy up to a cap, then releasing alt-fire would release a ranged energy blast that penetrates all zeds up to a set distance for full damage.
Normal punches are useful for easy to kill zeds like clots, heavy punches are good for stumbling zeds that are hard to get close to and melee without getting hurt (like crawlers, stalkers, and gorefasts) as well as killing medium zeds like husks and sirens SAFELY when they're in the middle of a horde (because the small zeds around them will get stumbled repeatedly as you wail on the medium zed), and the energy blast would be good for getting rid of groups of zeds or doing high ranged damage to large zeds.
A firebug weapon that does next to no impact damage, but leaves long lasting fire on the ground that damages and ignites zeds that walk through:
Firebug bores me because all the weapons are just spray at zeds and they die. This would center more around lighting up paths and choke points. It'd have more ammo than weapons like the flamethrower, but wouldn't have the dps capable of killing large zeds (since impact damage is low, spraying at a large zed does nothing but extend it's burn duration and put fire on the ground below it).