This thread was just starting to pick up steam... Anyway I neglected to weigh in, and I'm a massive film geek (not quite Catmatt level, though)
First of all, even though you're a chicken-tard, Goldbrick nailed it with John Carpenter's The Thing...Holy SH*T that movie kicks ass. The stop motion special effects still look better than any of the cgi garbage they have today.
Caddyshack is great, although it's sort of ubiquitous now so I can't call it underrated. (This here's Mr. Wang, no offense) Just watched it again last week. Did you know that originally it was supposed to be a serious film about class in america?
Now onto movies that got solidly rotten ratings:
UHF--Weird Al's finest, and for some reason only movie. Skip Be Kind, Rewind and watch this instead for a good movie spoof.
The 'Burbs--The height of Tom Hanks comedic career, even if he won't admit it. He became decidedly unfunny after this movie.
Kingdom of Heaven--A brooding Orlando Bloom stars in this epic about the Crusades, and he nearly ruins it for everyone else, but not quite. There is a directors cut that I haven't seen yet that actually got good reviews.
Premonition--This movie got like 8% tomatometer, but it's a good puzzle/freaky movie. The ending is unsatisfying and I think that pissed off every critic enough to give it a bad rating, otherwise it's a fun time-traveling romp.
PCU--Jon Favreau's finest acting performance
The Chase--Charlie Sheen when he was totally loaded
License to Drive--the Coreys' Oscar-caliber comedy.. about getting a driver's license
Summer School--From the days when we could take Mark Harmon seriously
high rated by critics, but nobody has seen:
Memento--If you thought Premonition sucked, well this movie is a lot better. Lenny!
Serenity--best sci fi movie of the 2000s
in Bruges--Don't ask questions, just rent it