Giant Goo:
Super large goo, drops normal sized on taking damage. Slow, but once it’s sighted a player, slowly builds up speed as long as it goes in a straight line - it’d be awesome if it could take up multiple tiles like a vehicle, have trouble turning, and crash through buildings then explode into multiple goos, but that seems a bit much.
Zs:
Juggernaut Zombie - slow, but stupidly armoured and healthed, basically to be a threat to vehicles if they crash into them.
Leaper zombies - basically hunters from L4D, zombies that leap like cougars at you.
Frozen Zombies - inflict frostbite on hits, put fires out around them
Hurler Zombie - size of a hulk, but not as fast or tough, instead throws other nearby zombies at you.
Horde magnet - some form of zombie that attracts others to it, uses them as shields, and heals them.