Darkfall. I dont need to list all the reasons. but i'll list a few for fun
Huge repeating world, no walls.
kill anyone anytime.
frikin pirate ships
variety of weapons, mounts, and races.
But...
9 gigs
15USD p/month
you might not be able to run it that well with all the 10,000 players and their fancy texture-filled armour. plus there are no repeating textures, so all that being rendered at once might lag you. there are no loading screens until you enter buildings.
you can die, and lose all your stuff :c