I've come up with lots of new suggestions lately: (more will be added later)
Missile pod:
Maybe could look something like this:
<picture> Maybe like that except smaller and would be hand/shoulder
mounted. Missiles should be small, not do that much damage, not explode very big, but not spread that much.
More zombie types:
Would really be zombies. I was thinking stuff like spiders, snakes, scorpion, bats, a swarm of bees/flys/mosquitos, a bandit, and maybe something else I can't remember right now.
Shopping cart: A shopping cart vehicle for a movie prop.
Less powerful (then the homing vector) homing weapon: Should only shoot one bullet at a time that can't go through things, just blow up on them. Also shouldn't go as fast and be able to turn as sharp as the homing vector's bullets.
(more ideas here) :S
Poll