I play this minecraft server, which is a "hardcore" pvp server, where you can destroy everything thats not been protected by a clan, steal everything you can, etc...
People can get together, form a clan and pay for a city which then renders the blocks unbreakable, but cities must have entry points.
Minecraft isnt all that, but this is the best server i found, beats playing alone.
http://www.thedarktide.net/