I'm gonna say Sket Dance takes the first place, followed up by a tie between Nichijou or Baka Test, and third place also a tie between Seitokai Yakuindomo and KonoSuba
Gintama executes their atmosphere pretty well, but they did alot of jokes, so I'll choose gintama... But for pure randomness, Nichijou is where it at, and Osomatsu too...
Nyarko both session's, mawaru pinguin drum, Arakawa under the bridge, Katanagatari, Mayo Chiki!, B-gata H-kei .......... I can atleast list 20 more but i dont want to.
Beelzebub, and School Rumble obviously. I just feel like the funniest times were when animes didn't try hard to make a comedy. Just some occasional comedy scenes once or twice every episode to break the ice.