Obviously you have such games as castle wars, ant game etc.. However something a little more sophisticated between the ticks =
www.projectp2p.net, as you play the game you can increase levels really fast what spend your time killing each other or monsters to gain rewards
if anyone takes me up on this game, I ll give free stuff to you personally etc to get ya started. It's a very enjoyable game and good for pvp (player v player) with some good ingame activities to defeast your opposition.
Anyways, any more info PM me or ask in this thread
CBA