Nichijou is the best/funniest comedy anime I've ever watched (although the mini series within nichijou I always skipped through cuz I thought it was retarded...but that's a very minor part of the show)
Hyakko
Hataraku Maou-sama
Yuru Yuri (although I found the second season to be...borderline unwatchable)
Hayate the Combat Butler (not asconstantly funny as the above ones, but has like 70 eps, so will keep you entertained much longer)
As for Gintama...I watched up to ~ep 50 and while it has it's moments I didnt find much of it very humorous...or very entertaining, but it's generally thought well of, so I'd recommend watching at least a few episodes to judge for yourself.