What are some movies you severely underestimated?

[LMU Uncle Alfred]

I didn't think that much at all about Shaun of the Dead because of the way it looked in the previews.  I thought it was just like those god awful scary movie parody movies.

Watching it the first time I didn't think too much about it either, but here I am several years later and now I think it's one of the funniest movies I've ever seen.