Blade & Soul is pretty fun although with higher level dungeons you'll want to know the mechs or you'll get booted fairly quick.
Tera's fun, F2P, the only bad part is some gender/race locked classes.
Soulworker is neat for a F2P anime MMORPG however the leveling is painfully slow IMO.
Closer is another F2P anime MMORPG but with a sidescrolling element to it. It's fun but appears to be lacking players as every time I try to get a team there's no one joining my quest even when the server is populated. This could also be due to my current level (18) as the majority of players I see are much higher.
Black Desert is a good game when it's on sale on Steam for $5. It has good mechanics and the story is decent but I got bored with it after awhile.
Vindictus is pretty good, F2P and where the game gets it's cash is from the costume shops which a full outfit (if you count underwear/costume & hair) will be about $30 which is actually reasonable at least for me as I've put about 80 hours into the game.