Everybody knows League of Legends, in this 5 vs 5 game, you can play arround with your friends fighting against eachother or against others.
In League of Legends, players assume the role of an unseen “summoner” that controls a “champion” with unique abilities and battle against a team of other players or computer-controlled champions. The goal is usually to destroy the opposing team’s “Nexus”, a structure that lies at the heart of a base protected by defensive structures, although other distinct game modes exist as well. Each League of Legends match is discrete, with all champions starting off fairly weak but increases in strength by accumulating items and experience over the course of the game. The champions and setting blend a variety of elements, including high fantasy, steampunk, and Lovecraftian horror.
This is an all free game you can download from their own website.
Click here for the game page