Ok, not a movie, but the SciFi (or Syfy, whatever) channel's Battlestar Galactica series -- this was the best thing ever, and I was really happy that they decided to wrap it up and give it an ending rather than drag it out till the ratings died. But the final season became totally lame, and irrational, and dragged out too long like they were just trying to fill in the required number of episodes. Left a lot of loose ends and inconsistencies too.
Reactions to other nominations:
Lord of the Rings -- I could feel during the final movie that the "scouring of the shire" wasn't coming, and I could tell that it just wouldn't have worked anyway. But you're all right, that ended up being the endless denouement. The original structure is supposed to be that you feel things gradually relaxing and going back to normal, then suddenly everything is all wrong at home. Didn't quite pan out. Without the scouring, Jackson should have just wrapped it up with Aragorn's coronation and maybe 120 seconds of life in the shire and the grey havens.
Monty Python and the Holy Grail -- I teach this movie sometimes in history classes. The ending isn't funny -- but I think it is very deliberate, and it gives the movie an edge and a relevance that it wouldn't have if they had ended on a regular gag or some conventional climax.
Watchmen -- Absolutely right. WHERE THE HELL IS MY GIANT SPACE SQUID!???