Jurassic Park. Its a childhood thing, it was the first movie I really loved. I had (and still have, somewhere in this house) toys for it and everything.
Other top favs are Shaun of the Dead, The Matrix series, most of the Godzilla movies, Wrongfully Accused (which will always remain the funniest movie in existence), War of the Worlds (2005), Silent Hill, Independence Day, Kill Bill, The Island, and probably a whole lot more I'm missing