When Harry Met Sally - it's my ultimate feel good film. I've watched it too many times to count, but it never fails to make me smile and I've never felt bored watching it. It's happy eneding edges out Roman Holiday, which I must have watched a similar number of times, but the ending of Roman Holiday, whilst making it more interesting, kills me.
I also love Breakfast at Tiffany's just because Audrey Hepburn and George Peppard are so beautiful it's mesmerising, although I prefer the short story.
Action film wise - Speed is always exciting, no matter how mnay times I watch it, and Keanu and Sandra Bullock have sparky chemistry, which gives it an extra something over other action films. I know it's slightly cheesy and the plot is the simplest plot you can come up with, but I always enjoy watch it.