What horror movie did you venture to watch with expectations of it being completely lame, but then it turned out to be really awesome?

If you’re gonna say something like, ’‘all of em lawlz’’ be my guest, but give a coherent, intelligent reason as to why.

That said, I watched Jennifer’s Body. I thought that it woulda been one of those lame horror films where nudity and guts are exploited for the sake of flash value more than anything else, like many horror films are wont to present, but this was actually pretty good, and while cheesy, the story holds itself together quite well, full of corny moments, lame one liners, creepy memories and funky symbolism. And guts ahoy!
The end climax is also quite neat, considering it involves an Exacto knife.

Got one? Explain?