Shivers or They Came from Within is David Cronenberg's controversial first film. Combining elements of zombies, nymphomania as well as weird slugs they film holds up incredibly well. If you can buy the premise that the major players share a single massive apartment there is much to enjoy here. The practical effects are great in there subtlety and the eerie atmosphere is top notch. This flick is pretty difficult to find for a reasonable price and impossible to rent, but you can stream it here.
Funding for the film was acquired using a Canadian tax dollars and people were outraged when they saw the final product. Despite this outrage it's the only flick funded with this program that turned a profit.