A couple years ago when "Traffic" came out on DVD, we somehow got a copy of it in the box of the movie we actually wanted-guess the store employee screwed up. Anyway, we put it in, and watched about 10 or 15 minutes of it...then put it back in the box and took it to the store to get the movie we actually had wanted. Pretty bad when you don't watch a movie you could have watched for free. (Yeah, I know, it won some awards or something, and critics thought it was great-blah.)
Another time we rented an anime that looked interesting from the cover art and the description on the back. I don't remember the title of it, but it had Lil' Kim as one of the voice talents, and it was about superheroes being outlawed because they were dangerous to humanity. It was awful. The animation was elementary at best, and the plot was a stinker too. We made it through about 15 minutes of that, and took it out of the DVD player.
I'd probably have Battlefield Earth on my list too, but I never even watched it since I usually steer clear of anything with Travolta in it, anyway. The one exception to that recently was Swordfish, which I basically rented only because it had Halle Barry in it, despite knowing that Travolta was in it too. I was presently surprised that it was pretty good.