It's called Adventure Time Battle Party, which you can find
here. It's a browser game yeah, but it's not that bad. You only have 3 moves though(2 regular ones and an ult.) In addition to the usual nuke enemy towers, it also has a point system where CSing, getting kills, and taking tower get you a certain amount of points, and whoever has the most at the end of the 15 min. time limit wins.
You can also jungle Gunther.
Unfortunately, since it's on CN, the chat system sucks. I could use more people to help me defend against the evil proxy magic men though.