Asobi ni iku Yo! is my favorite slice-of-life catgirl anime and while it's retarded it's easily one of the comfiest things I've ever watched.
Golden Boy and Ghost Stories are also notable for being the only dubs I actually prefer over the subs since in GB's case it's just excellent and in GS's case it's really funny.
Gunsmith Cats is not the incredible masterpiece that people say it was, but it was really entertaining and I like to go back to it pretty often.
Legend of the Galactic Heroes isn't just a good space opera as >>58
said, in my opinion it's the best
space opera there is - an excellent show that shows all sides of an enormous, galaxy-spanning war.
Space Battleship Yamato and its remake aren't bad and while I wouldn't watch them again, I'm glad I watched them once.
Patlabor was the very first anime I ever watched and I may be biased but I think it's awesome.
Final Fantasy Unlimited is a dumb show but I enjoyed it anyway.
Azumanga Daioh! is another weird one, but lots of people seem to enjoy it. It's hard to explain but I love it.