Any anime with lots of guns? or zombies. Or vampires.

Or all? xD

trigun [gun]
gunslinger girl [gun]
trinity blood [vampire]
hellsing [i think it has all]
vampire knight [vampire, gun]
black cat [gun]

Vampire Hunter D

Karin

Vampire Princess Miyu

Tsukiyomi Moon Phase (Hmm.. not really vampiric..)

Princess Resurrection

zombie-loan[Zombie-gun]
Black lagoon {gun}

Shingetsutan Tsukihime (Vampires)

Gantz (Guns, vampires in the manga) (the anime doesn't compare to the manga)

Gun x Sword ? = )

Cowboy Bebop...
Eh futuristic explosive laser cannon's close enough...

Black Cat
Black Lagoon
Trigun
GunXSword
Gunslinger Girl
Gantz
Monster