Seeing as I'm the most obscure and massive movie guru, there's absolutely no way I'd ever be able to do 'a few favorites' picking from any genre. However, I could go genre-by-genre, and such would be as so:
Overall beef supreme winner of the best movie ever no matter what:
Blues Brothers
Horror:
Silence of the Lambs - Hands down, best horror movie of all time.
Drama:
Seabiscuit - I don't know why, but I've always loved this movie, even though it's pretty much forgotten by now.
Comedy:
Life of Brian - Duh. OR
Idiocracy - Both are amazingly funny satires and very clever as well as gut-bustingly hilarious.
Action:
Indiana Jones and the Last Crusade - Indiana Jones has to be one of my favorite characters due to the comedy and his portrayal of cynicism, and I always thought that the Last Crusade had the most interesting plot of them all.
Suspense/Mystery:
The Rope - Hitchcock is an absolute genius, and this movie always keeps you on your toes. OR
Brick - I can almost guarantee that nobody's ever heard of this movie, but it was pretty fucking great. Epitome of an indie flick, and all the actors were splendid, the story was tight, and everything fit so well.
Musical (excluding Blues Brothers):
Moulin Rouge - While most guys are turned off by the very nature of the movie, it's actually very well-constructed and interesting--from the visual exaggerations to the acting.
Cult Classic:
Donnie Darko - It's a tough race between this and Rocky Horror Picture Show, but I had to go with Darko, because it's just so...strange...and it really gets your mind pumping philisophically, trying to analyze the story which I like the best about it.
Of course there are so many more that I could add onto these lists, but it would take ages to spout my favorite movies, so I'm not even going to bother.
~D-Draw