Welcome to the NHK was really funny so many hilarious moments in it, like the part with the FFXI parody where he was gonna do RMT (if you played FFXI you probably would find it even more funny cause alot of stuff about it is true.)
Genshiken was pretty funny too.
And One piece, dont think ive laughed as much watching other anime as i have with one piece tho it may just be casue there is somany episodes, Luffy just makes me laugh so much even tho to some it just stupid humor it is but it just really funny to me. i cant pick one -_-.....
A lot of funny anime around ... so im just going to say the last 2 i saw that realy cracked me up :)) : Green Green and Club to death angel Dokuro-chan
Other from those ... some other series that made me laugh with tears : Lucky Star , Kanon 2006 , Clannad , The melancholy of suzumiya haruhi , Full metal panic fumoffu , Zero no tsukaima , School rumble , Love hina , Nagasarete airantou , Chrono crusade .... and many more
clannad (tv series)when sunohara face is hit by the starfish of Fuko ibuki and when fuko-chan is taken to place she doesnt know or when tomoya always plays jokes on fu-chan
touka Gettan(When momoka is eating food and can even catch it)