when I was a kid and young woman, it was "It's A Wonderful Life" hands-down - I would watch every showing in December (and there were a LOT of them in the days before VCRs and DVDs).
Recently "Galaxy Quest" is highest in my DVD rotation, although I like to re-watch TV series on DVD.
When I used to make costumes, I watched the Salkind brothers "3 & 4 Musketeers" (With Faye Dunaway as Milady DeWinter) - amazing costumes.
I will also pop in the extended versions of "Lord of the Rings" or "Star Wars" (episodes 4-6) If I want something on while I'm sewing.