Action / RPG MMO
Ghost X - free to play 3D sci-fi MMORPG set in an Urban Metro environment where players have fight against evil demons in mostly instanced environments.
Dragon Nest - free-to-play fantasy MMORPG developed by Eyedentity. It uses a non-targeting combat system ensuring that players have complete control over every single one of their character's movements.
Dragon Nest requires users to advance their characters by teaming up and traveling into instanced dungeons.
Honestly, I wouldn't recommend any other MMO under this genre atm.
And even these ones will probably get boring after a little while.