I loved playing Dofus for the short amount of time that I could without shelling out.

Every now and then they open up an F2P server... but then its only a short time before said server goes P2P.

+1 for the battle system (love the Final Fantasy Tactics-esque system), -3463784638 for turning 100% P2P every so often.

It's also a flash based game. Not sure if that really matters, but I noticed that nobody mentioned it before.