Risk Your Life, a 2004 MMORPG, Relaunches as Return of Warrior
While I can't imagine this new official version of the game bustling with players, Risk your Life was quite successful when it launched in 2004, reaching over 125,000 ed players in North America a few months after launch with over 1.25m players worldwide (as of 2005). The game features over 16 classes and like many older MMORPGs, has a strong emphasis on PvP.
Further reading: Official website