If you like Sci-fi first person shooters (can also Mutate into 3rd person shooter) . This game is the perfect MP FPS.
The UT3 Editor that comes with the PC version is a wonderfull tool , along with some programs like photoshop, Maya , Zbrush, 3DSMax you can make virtually any type of character/weapon/map mods with custom textures which is great. Talented Modders have already made and posted many great mods that range from a top down shooter, a SSBB type 2D gametype, real life weapons AK-47, Character mods such as , Cloud and Zack, Old Snake, Master Chief, Spawn , Samus, Crysis suit, Bender, etc. There are also more map mods then I care to count and alot of them are genius.
My favorite part of UT3 is the fast paced killing and the announcer dude who says Killing Spree , Double kill , Multikill. Headshot and so on. The sound is really great and with good speakers its awesome. The Graphics are awesome as well the Sci fi maps are beauty's. If you like sci- fi fps this should be at the center of your collection.