As dvdjunkie said, it's hard to pick a favorite when there are so many I will rewatch when the mood strikes.
A short list (based on my 10s and a few 9s at IMDB):
If anyone cares, here is that list:
http://www.imdb.com/mymovies/list?l=9421458
No order, and there may be some favorites I haven't actually rated.
Also, I left off some, as they may be films that I consider "great", but not "favorites". A few of the 9s and 10s are great films that are probably destined to become favorites, but for whatever reason I've only seen them once so far (like Hot Fuzz.) Also, there may be some in the 6s, 7s, 8s and 9s that aren't necessarily "great" films, but are still films I love to rewatch. Plus, my ratings are purely subjective and I may have rated one film in comparison to another, that doesn't necessarily mean I would consider it great or not great kist because of it's position on the IMDB list. A rating may change from one viewing to the next, although I may not bother to change the vote at IMDB.
Most anything above a 5-6 I consider rewatchable, and most things 4 and below range from "probably never see again" to "complete dreck that wasted 2 hours of my life." There are also a few 1s tossed in on films I haven't seen that I feel truly deserve that rating based just on the trailer, or other considerations.
I left off Disney, but I think there are a few Pixar films mixed in there, sorry!
I'm sorry I didn't write a reason for liking each one, I'd be here all night if I did.
Blazing Saddles (1974)
Bud Abbott & Lou Costello Meet Frankenstein (1948)
Duck Soup (1933)
The Gold Rush (1925)
Groundhog Day (1993)
The Ice Pirates (1984) - probably the lowest rated of my 10s! It has a 5.2 rating at IMDB!

The Incredibles (2004)
Kung Fu Hustle (2004)
Lili (1953)
Miracle on 34th Street (1947)
Modern Times (1936)
The Music Man (1962)
My Neighbor Totoro (1988)
The Producers (1968)
Ratatouille (2007)
Scrooged (1988)
Sleuth (1972)
Spirited Away (2001)
Singin' in the Rain (1952)
Wall*E (2008)
White Christmas (1954)
Young Frankenstein (1974)
Shorts:
Wallace & Gromit - Particularly The Wrong Trousers, although I like all of the shorts, and the movie.
Anime OVA:
Panda Go Panda - This wonderful 2 episode OVA series from Miyazaki and other Ghibli folks is great, and I've rated both episodes a 10.