IMO; I really like Demon's Breeze for its completely unique gameplay because of the fact you have to watch every step you take. It isn't because of the bridges, it is more or less because of the holes, they aren't evenly spread out so you don't know when/where to dodge them, it's a fun new aspect brought into play.
I also am I big fan of Survival Kingdom, I have only recently been attracted to it by its creativity that I didn't realise in the first few times I played it. It has so many fun traps that lead to death if you fail, or reward you with so really useful items that could help you reach your chances in winning by quite a lot.
Another I still like is SG4, reason being: everyone is stacked. This results in epic PvP battles where nothing is unfair in gear wise. Matches are quite quick as well so it's fun to play it every now and then, but definitely not all the time though.