This is such a hard question - there are so many good films, my favourites change all the time!

Strangely, I find it easier to remember my least favourite films:
Blackhawk Down - botch-job US-style becomes box-office hit
AI - nearly accidentally slashed my wrists at the end of this one

But here are three of my favourites:

American Beauty - unconventional and deliciously disfunctional
Amelie - heartwarming
and then there's a toss-up between The Matrix (groundbreaking) and Mr & Mrs Smith - sizzling! not the greatest plot, but it's hard to decide which one is more fanciable!!