I loved the Pink Panther movies, but my all time favorite was The Great Race with Tony Curtis, Natalie Wood, Jack Lemmon, Ross Martin, Larry Storch, Dorothy Provine, Keenan Wynn....my family watched that at regular intervals for years, and we still do occasionally.
Lemmon's dual role in that movie (Professor Fate and the drunken prince) was a classic...and the giant pie fight was a landmark in cinema!
IMO one of the most fun movies ever made. http://www.imdb.com/title/tt0059243/