Avengers: Earth's Mightiest Heroes (only seen the first season, and unfortunately I hear the second season isn't as good), Legend of Korra, and of course the obligatory Ponies, although I don't watch the show anymore. Caught a few episodes of Young Justice which seemed cool, except for one characters incredibly annoying catchphrase (fans know who I'm talking about). And I have seen some of Adventure Time and really enjoyed it, but I have yet to watch more than the occasional episode with a friend.
I assume you're talking about kids shows, but if not I'll add my voice to those saying Archer and Metalocalypse. Archer is one of my favourite shows, no qualifications. I'll have to check out Gravity Falls, it looks pretty cool.