No one has mentioned "Harvey" yet!
Another one from a few years ago I enjoyed was "The Man who came to dinner" - could never find it on video, fortunately either TVO or PBS showed it.
3 with musical themes are the 2 mentioned above "Commitments" and "Spinal Tap" but I'll also add "Lenigrad Cowboys do America"
Funniest for me include "Afterhours" and "No Surrender" and lots of the Ealing Comedies.
Movies I can watch over and over again are Casablance, Sims - "Christmas Carol", "Dr. Strangelove"
Movies I have spent ages trying to get the video include: "Picnic at Hanging Rock" - probably the most 'lyrical' for me if that makes sense and you know what I mean, "Aguirre, the Wrath of God" - worth it for the first 10 minutes alone, and also by Herzog - "Nosferatu"
Add films like "Usual Suspects" and "Resevoir Dogs" and the list goes on!
I'm sure I've missed a lot and people above have mentioned many I enjoy. 2001 is the film I've seen the most but I haven't seen it for years.