Soulsplit or Battlescape.
However, both have their bad points.
Soulsplit Economy is an absolute mess and has bugs that have been in-game for a very long time. The owner also seems to care very little about fixing these.
Battlescape has probably the worst community I've ever seen in an online game. It's full of childish people constantly arguing, and then there's the clans.. never have I seen anyone with such large ego.