Hm, that's a tough one. I'd have to say the part in Clannad (or Clannad After Story. Can't remember) where Tomoya tells Nagisa that Sunohara is in love with Tomoya, and Nagisa gets all flustered and panics everytime Sunohara tries talking to her. xDD
Second funniest would probably be the whole, "AND A TOILET SEAT!" conversation that Sunohara had with Tomoya. I crack up everytime I see it. XD

