I like NWN because of the server/module system... its like Half-Life, it can be modded(in a way) and the servers are hosted by people, which means rules vary.
Aventia was my favorite module/server, and I stopped playing NWN for awhile then when I got back on Aventia was like 50x larger, the module size was like 100mb. It is still private, but oh well
I used to 'legit duel' on NWN, which consists of editing your gear to the best possible config without any immunities or unlimited spell casting staff type things. There were a few other restrictions but I forgot. Oh, and you couldn't mix Paladin with other classes because of the holy damage ..