Dungeons N Dragons online, the only MMo ive liked, been playing on/off since beta which was just over 3 years ago.
Have tried trials and betas of other games but none really grab me like DDO did, its not everyones cup of tea as pvp is limited ( which i think is good) the quests are all instanced, so no one outside your party can enter ( another good point imo), xp is based on quest completion and any optionals, not per kill as in most mmos, mods are currenlty free, should be getting mod 9 in the next month or so, which will raise the lvl cap to 20.
Downside is there is some grinding involved due the crafting that was introduced, but then you dont need to grind if you dont really care about the uber items, like myself.