War of the Worlds (the Tom Cruise one). My wife and I watched this on DVD a couple months ago, and both came to the conclusion it was the worst movie we'd ever seen. I just can't believe how bad it was. The acting was awful, the effects were crappy, and the plot holes were so big you could drive a mack truck through them.
Couple examples (not real big spoilers):
At the beginning of the movie, the "storm" knocks out all electrical devices. I mean everything. The power is out, cars won't run, cellphones don't work, etc.. Just a minute or so after this, the camera pans directly to a guy who is taking pictures of the alien machine with his working digital camera. I mean seriously, has does someone not catch that?
And hey, let's fix a car with a completely fried ECU by replacing the starter solenoid. Yeah, that'll do it, and not a single other person in the world (except for the military) will realize this, so we'll have the only working car.
It's crap that like that made us cringe about every 5 minutes, but we forced ourselves to sit through the whole thing. We kept expecting it to get better, but man, it only got worse.