Bunman, AKA 'The Untold Story'
Mordum (and probably anything else from ToeTag Productions)
Seed (not a great film, after all it is Uwe Boll, but elements of that film stay with you, like the hammer scene)
The Human Centipede (fantastic film, saw it at last year's Frightfest!)
A lot of people here recommend Salo. I do have it on bluray, but time has not been good to that film, and if I'm honest I found it a little dull and a bit ridiculous, although I am interested in the real history of that period, particularly as one side of my family came from North Italy.
Edit: As a side note if you want a really 'out there' fun film, Vampire Girl vs. Frankenstein Girl' gets released on DVD next month. Saw it at Frightfest and loved it!