My Bride is a Mermaid or Seto no Hanayome had me in stitches in the first two episodes, then the laughs stopped so hard, but man those two eps were awesome
The funniest anime I've ever seen is definitely Great Teacher Onizuka without a doubt. It's about a ex delinquent who wishes to be a teacher because he wanna see high school girls, very funny. I recommend watching it if you like funny/comedy animes!
Out of the 830+ animu titles I've seen. Danshi Koukousei no Nichijou or Daily Lives of High School Boys is my pick. I've never laughed at an anime so much in my entire life. Its so funny I specifically watch it when I feel like I need a pick-up laugh.