If you want to go with 'funny' actors, then most of Judd Appatows regular type cast are genuinly funny people(because they do a lot of improv in the movie)
Paul Rudd is funny as shit in cedar house rules
Steve Carrell
Jim Carrey
Chris Rock(sorta act but he does a lot of his own jokes and shit in movies)
The fat woman from bridesmaids, the heat and her little role in the hangover three where she works in the pawn shop
Adam Sandler(pre-2004) his stuff was comedy gold, now...ehhh...yeah.
Rob Shnieder or whatever, hes amusing
Leslie Nielsen(Rest In Peace) for being the king.
Ryan Reynolds(not a comedy actor so to speak but hes well rounded and can make you giggle and chuckle)
Robert Downey Jr had me laughing out loud in Tropic Thunder and his Sarcastic & Satrical humor in Iron Man, but his performance in Sherlock Holmes was brilliant
Woody Harrelson simply because of zombieland, "TWINKY!!!"
Eddie Murphy of course, hes funny on and off screen
Theres plenty more just cant be bothered anymore lol