Films that have had me rolling on the floor in stitches: Trading Places, Coming to America, The Mask, Dumb and Dumber, any of the Laurel and Hardy films, likewise any of the Chevy Chase National Lampoon films, The Rocky Horror Picture Show, Withnail and I, Shakespeare in Love, Priscilla: Queen of the Desert...amongst others.
Films that I can't watch without sobbing: Disney films, War Horse, Black Beauty, UP, the Lord of the Rings trilogy, The Colour Purple, Quills, The Hunchback of Notre Dame (1939), Gone with the Wind, The Green Mile, Ed Wood, The Elephant Man, Arthur, The Orphanage, Pan's Labyrinth, Amadeus...and many many more.
My favourite horror films: An American Werewolf in London, The Howling, Dog Soldiers, The Descent, The Exorcist, JAWS, The Thing, Rosemary's Baby, The Omen, The Devils, Haxan, Blood on Satan's Claw, The Amityville Horror, The Witchfinder General...there are lots more, but these are the ones that come to mind at the moment.