If I'm flipping channels just looking for anything, if I run across the following I feel obligated to watch:
The Fast and the Furious
Any of the Harry Potter films
If there isn't a new film out on DVD that I want to watch, and I go to the shelf, I usually end up with something from Kevin Smith, like Mallrats or Clerks. If not that, then one of the following;
Harold and Kumar go to White Castle
Or a super hero film like the X-Men, Spider-Man or something similar.