I probably laughed at most of the comic films suggested thus far including the Police Acadamy ones and the Carry On's as well.
However mostly the times when I've ended up on the floor really peeing myself laughing have been when reading books such as Indecent Exposure or Wilt by Tom Sharpe.Or the Spellsinger books by Alan Dean Foster as well as a few Terry Pratchetts and The Hitchiker's Guide to the Galaxy plus The Stainless Steel Rat series by Harry Harrison(and Bill the Galactic Hero).I think the pictures I see in my mind are much funnier than the ones I see on screen.