Just thought I'd see what films ADISC likes.
Personally most of my favourites are comedies, but my all time favourite film has to be the Lord of the Rings trilogy. Excellent attention to detail, made it exciting while (roughly) sticking to the book, excellent soundtrack, excellent actors, and the camaraderie between everyone backstage during the making of is amazing.
Aside from that, my favourite films are:
Monty Python's The Holy Grail
The Marx Brother's Duck Soup
The Longest Yard (Burt Reynolds version)
Hot Shots!: Part Deux
Reign of Fire