well if you like old films (i do... you may have noticed)...
Les Tontons Flingueurs is an absolute jewel of a gangster comedy. i'm not honestly sure how well it will work for non-francophones, because the dialogues were written by the all-time master of dialogue, Michel Audiard, and use lots of slang and idioms, but it's worth watching anyway. Another absolutely brilliant one is
Drôle de Drame (i lent my dvd of that to someone over 2 years ago and haven't gotten it back yet
), that's a top of the list one as well. and one of my all-time favorites (not a comedy) is
Jean Cocteau's Orphée (Orpheus). if you like suspense,
Les Diaboliques, worthy of hitchcock. and if you want to see the heist turned into an art form don't miss
Le Cercle Rouge which takes robbery to new heights of elegance (starring Alain Delon, by the way, France's major heartthrob actor from the 60's, and Yves Montand). you'll be cheering for the bad guys, seriously.