Or if you're looking for a TPS shooter, more like GTA but battle between thugs and cops, you can try APB Reloaded. It's really not that bad. It's not room based, but open world like GTA. You can choose to play cop or thug and load yourself with weapons and roam around the city. The last time I've played it, I was with about 20 cops and 30 thugs in one area. (I accidentally passed by)
Dragon Nest has a pretty large community as well, it's a dungeon based game, but there's PvP system too but room based. Pretty intense with skill cooldowns 'cause you'll be spamming your skill keys for an immediate execution after cooldowns. Also TPS viewed.
Or if you'd rather a more anime-style like PvP game, I'd recommend Grand Chase Online. It's a fighting game, no guns I think (I haven't came across one when playing) but it seems somewhat like a small community to me.
MU Online is a top-bottom view, point and click game with skills on keyboard. This game is a medium sized community and is a pretty old game. But it has a PvP (Duel) function where you can request another player to duel with you. It's not room based so you can practically run everywhere. If you rather not duel, you can just immediately attack the player, which makes you an outlaw and your character will be glowing red. If you kill an outlaw you get to take his items. But as usual, you can't attack players in town. You usually have to wait about 3 hours online before you no longer will be an outlaw anymore.
Dragon Saga (Dragonica) Is a unique 3D side scroller view game with a unique style of playing. It has PvP too but a small player-base. It used have a large player-base but for some reason, their SEA servers went down, and other servers began to exacerbate. I'm not sure if I played in the wrong server, but there's two companies that publishes Dragon Saga. Maybe I was in the one with lesser players.
Rakion Online is a medieval-age game (Swords, Knives, Staffs) where you mainly PvP with players. It's rather tough and is also room-based. You can do AI mode too.
Or if you're looking for a FPS, I would definitely recommend Blacklight Retribution. One of the most unique FPS I've played. There's really too many features which makes it unique compared to other FPS but the most intriguing feature is the weapon customization feature. It's not like any other FPS game, where if you buy a particular gun, you own the game. No, in Blacklight everyone will start with the same gun, and you can customize your gun based on your choice. Eg. Muzzle, Ammo clip (capacity), Scope, and etc. There's a suit where you can sit on like MechWarrior as well but requires you to kill an amount of players in the game.








