What the hell dude? The worst movie of all time is 'Manos', the Hand of Fate.
A lot of these movies are pretty bad but not horrible (Pearl Harbor, Signs, Day after Tomorrow), and Requiem for a Dream is actually good.
Here are some bad movies:
Mod [censored] Explosion
Meet the Feebles
'Manos' the Hands of Fate
If you want a more modern movie that's really horrible,
here it is.