Yotsuba&! is one I haven't seen mentioned that I like. The main character is like 5 years old, and thinks every mundane thing is this grand adventure (Like thinking she's some tough bad guy when she's carrying around a watergun). She's also generally causing trouble for everyone.
Unlike Azumanga, which was made by the same person, Yotsuba is pretty much based on chapters rather than 4 panel stuff. Only a manga though, no anime so far.
Other than that, I'll go with the usual Haruhi and Spirited Away. There aren't really too many others that I like or even watch. I thought the first 14 episodes of Gurren Lagann were okay, if a bit too fast paced near the end of it, but after that I didn't really care for it.