One of my very favorite games on my iPhone. This game is just so much fun and keeps expanding with new teams and other various content. Just added and one I have yet to try is the Shaolin team.
This game is also available on Steam, and if you purchase on Steam you will gain access to the Team Fortress 2 team as well as unlocking The Hero Academy team within Team Fortress 2. Great cross promotion work there! This game is very easy to pick up and play, but much more difficult to master!