If we're gonna go with a comedy (especially with John Candy), I hafta say Planes, Trains, and Automobiles. I was actually in pain from laughing so hard after the first time I saw that movie.
As far as all time favorite(s), especially from my formative years, absolutely GOTTA go with Star Wars (particularly Empire Strikes Back). My parents and I went to see it at the drive-in when it first came out. I called the Lightsabres "Dangerous Flashlights". I think I was about 4 years old?... I may be dating myself as well, but not so bad as 2001: Space odyssey..DAMN! might as well have said "The Entertainer".

-Tavis

'99 SVT Contour #535/2760, born 11/30/98. Toreador Red / Prairie Tan Wife's car: '00 Saturn LS2. Dk. Toreador Red (no joke) / Graphite Sunday Bruiser: '67 Camaro rs/SS350 4 spd. Ermine White / Custom Yellow