I'm going to recommend the English subbed version of Azumanga Daioh, because Osaka's English voice acting made my ears bleed.
That, and Bokusatsu Tenshi Dokuro-Chan is great if you like random bouts of extreme violence played off for laughs, which I most certainly did.
I haven't actually watched Gintama, but everything I've heard, and what I have seen of it was pretty good.
Oh, and if you're into complete and utter insanity that is actually used to prove a point, but aren't interested in following a plotline, then I'd definitely recommed Sayonara Zetsubou Sensei.