I've heard bad things about, but never saw:

Gigli
Battleifield Earth
Catwoman ("...let's put it this way: Halle Berry in a skin-tight catsuit couldn't save it...")

Did see, and hated:

Weather Man -- you know it's bad when a sex scene can't save it (the Oktoberfest gal)
Eragon -- coulda been written by a computer, or a committee
Ghost Rider -- ditto