I fell asleep during Transformers: Revenge of the Fallen...
Only time I fell asleep to in the theater... Only time. I watched it again when it came out online and I didn't think it was that bad.
I remember going to see Hellboy II: The Golden Army with a bunch of friends cause we had nothing better to do on a lame ass night. By the end they wanted to murk themselves for watching it but I'll admit that it's one of my guilty pleasures, movie-wise.
I saw RED (2010) and 10,000 BC (2008) in theaters as well... Not saying they're bad movies, I just don't remember them at all.