Love Galaxy Quest. It's one of my top Alan Rickman movies: goofy fun that pokes fun at his dramatic persona. He was perfect for that character.
I was about to list off my favorite roles but there's too many. Right not Truly, Madly, Deeply is on my mind but I don't know if I can bring myself to watch it.

Funny that my Therapist asked me about imaginary parents recently because he was my Imaginary Dad, well one of them, for a very long time.