I'm no expert but I found Drunken Master II to be his funniest

I cant say I find any lucky star film that funny. the recurring theme of
contriving a way to molest women in a rented house
is so dumb. They have couple of moments like the paper scissor stone dance they do to decide who gets a bed.
Im quite fond of city hunter, its so bizarre I really like it.
I find project A and Operation Condor pretty funny, most of the humour is derived from the action sequences rather than the stuff in between.
The mans tongue didnt come through customs!

The Lucky Stars films : "Winners and Sinners"," My Lucky Stars" and "Twinkle Twinkle Lucky Stars"
there are other funny claasics like "Police Story" "Project A", "The young Master" and of course "Drunken Master" etc etc but just for pure amounts of actual comedic sequences the lucky stars films are the way to go. Also "City Hunter" is pretty much just a very silly comedy with bits of action in there but I find it to be a mostly awful film (cool street fighter sequence though and fun production design)
Peace