All of Donald's and Goofy's are awesome, but my favorites are Toot, Whistle, Plunk and Boom, Ben and Me, Paul Bunyan, Pecos Bill (I know that was in Melody Time but I still consider it a short), and I can't think of all the other great ones...:hammer:
If we're talking shorts, there's a Donald Duck one called "Duck Pimples." It's definitely my favorite for no reason other than it scared me yet made me laugh hysterically when I was little and it really stuck with me.
Oh and all of Goofy's "How To" series, especially "How to Dance" ... and anything with Chip and Dale ... or Huey Duey and Louie...
I just love cartoons.