Planetside, an all PvP (player-vs-player) MMOG. There are no NPC in this one at all! Everything you do is against a human element, you will never want to go back to PvE again.  I have never been a fan of first-person shooters, never enjoyed playing them.  A friend of mine gave me a 20 day trial and it’s all it took, I was instantly hooked.  This is, without a doubt, one of my favorite games of all times.

Try here for unlimited play up to battle rank 6.  You get a chance to try almost everything in the game, and it never expires.