I'm not sure which of these titles you've probably watched before, but:

I heard Gintama is pretty good, but I have yet to watch it.

Some I've watched are:

Angel Beats, very funny moments

Arakawa Under the Bridge (2 seasons)

Druaga no Tou: The Aegis of Uruk (2 seasons) This made me laugh pretty hard at times. The first episode of the first season is a troll so don't take it seriously.

Ben-To, ecchi and the usual stuff, it was okay to me. You might appreciate more as a guy.

FLCL

Ixion Saga DT, just finished airing this week. Hilarious self insert.

Jinrui wa Suitai Shima****a, looks are deceiving XD...

Kami nomi zo Shiru Sekai, nice twist on the harem aspect

Kuragehime, a very funny, but underrated josei anime

Tengen Toppa Gurren Lagann, you probably heard or watched this one already

http://myanimelist.net/animelist/Ardamaeus

^ You can look up the titles on my anime list and see the score I gave it and click on the title for the description of it on the site.

I've personally found that the shows with the most effective comedy could generally also be considered other genres... drama, for instance. Comedy is hard to keep funny for long on its own, although there are some shows which manage it.

On the more seinen/shounen ("male") side I would mention:

Sayonara Zetsubou Sensei (dark parody humor done correctly)

Cromartie High School (ridiculous, dumb, and endlessly entertaining)

Gintama (echoing KuroNyankoSensei here, but I've seen 30-some episodes and while I didn't enjoy the first couple of episodes, it became one of the only shows which manages to keep parody continually amusing for me)

One Piece (this one is controversial, because haters are just plain going to hate, but this show is bizarrely good once it "clicks." It can take a while, but I swear it does become an endless source of comedy, eventually with other genres woven in well)

Detroit Metal City (particularly good if you listen to metal music, extremely irreverent/offensive humor)

Yondemasu yo, Azazel-san (just to include a currently a more recent show... quite immature, but strangely funny, albeit also quite offensive)

And on the less "manly" side:

Axis Powers Hetalia (parody of historical events and international relationships)

Azumanga Daioh (classic slice of life about schoolgirls)

Ouran High School Host Club (technically a reverse harem romance, but one of the best comedies I've seen)

Yakitate!! Japan (cooking anime - just all-around great humor)


Hope some of these help as well!

Baka and Test is freakin' hilarious. School based comedy about misfits rising up to claim their rightful place in academy.

I agree with Ouran and Hetalia.

One that I'm kind of shocked nobody has mentioned yet (well, if they did, I didn't see it because I'm not wearing glasses and everything is fuzzy) is Lucky Star. I loved that one!

I really liked Gintama.
-School Rumble (Freakin hilarious!)
- Full Metal Panic? Fumoffu
-Good Luck Girl (was a little 'meh' here and there, but some scenes had me cracking up)


Sorry if these were repeats. I didn't see them.

Eyeshield 21 <<< I completely forgot this existed! haha

Right now my favorite comedy is Team Four Star DBZ Abridged.
There is also Full Metal Panic Fumoffu..