Very addicting remake of DOTA, an old custom map game from Warcraft III: Frozen Throne that is free to download
The ONLY problem with the game is if you solo queue for a ranked game, you normally end up in a very one sided game which is disappointing.
The BEST part is that it is constantly updated and the game itself is free! Most everything in the game can be bought with virtual money that you earn by playing games. You make this regardless of whether you win or lose, just twice as much if you win. The game itself is also free to download. The only thing in the game that costs money are the skins for champions and they go on sale constantly so they only cost a few dollars. You can also spend money if you don't want to wait to accumulate IP(in-game money)