Re-animator is very good. Oddly enough, I hear the theatrical version is better than the unrated, though tracking down a copy of that is a royal pain.
Cemetery Man, though that is not specifically zombie related.
Dead Alive has zombies and tanker trucks of gore.
The Beyond is strange but not bad. Same for Demons.
Tombs of the Blind Dead, very creepy.
If you want obscure, unusual zombie fare, look to Italian horror cinema. Though finding good stuff amongst the mountains of crap will take some doing.