Although it's easy to admire the maniacal glee of director Peter Jackson's bloodfest, Dead Alive is nonetheless intense and profoundly disturbing (edit - or simply ridiculous, over the top and downright hilarious, depending on your perspective). When a Sumatran rat-monkey bites Lionel Cosgrove's mother, she's transformed into a zombie. She begins killing (and transforming) the entire town while Lionel races to keep things under control.
(edit - also known as "Brain Dead". The British censors left it completely uncut - probably because it was so over the top silly - and if you cut the gore out there wouldn't be anything left to watch!).