This is a list of some common acronyms you may encounter being used in your travels as a gamer. Not all of these are isolated to just games, but are covered since you may still come across them while playing.

Acronym Meaning
AFAIK As Far As I Know
AFK Away From Keyboard
BRB Be Right Back
BSU Blow Shit Up
CC Crowd Control. Refers to abilities and spells used to keep groups of enemies from overwhelming players.
CG Congratulations
DC Disconnect (also d/c)
DD Damage Dealer. A class that deals damage. Also used as a verb meaning to deal damage.
DOT Damage Over Time. Refers to spells that deal extra damage at intervals after the initial cast (poison/bleed is a common dot).
DPS Damage Per Second. Refers to the amount of consistent melee damage output of a player/monster. Occasionally used to refer to a damage dealing class
FTL For The Loss
FTW For The Win
FWIW For What It’s Worth
GG Good Game
GJ Good Job
GM Game Master. These are players/characters that work for the games developer and are generally the in-game equivalent of a customer service representative.
GN Good Night
GTG Got To Go. Some people also use this as Good To Go (as in “ready”) creating some degree of confusion.
HP Hit Points. Generally, you don’t want to lose these.
IDC I Don’t Care
IDK I Don’t Know
IDR I Don’t Remember
IIRC If I Remember/Recall Correctly
IKR I Know, Right?
LFG Looking For Group (synonymous with LFP)
LFM Looking For Member
LFP Looking For Party (synonymous with LFG)
LMK Let Me Know
LOS Line Of Site. A technique of pulling a mob or group of mobs which typically involves an initial ranged attack followed by moving around a corner. Usually used to get a spread out group of mobs to bunch together, making it easier to use AOE spells and abilities.
MDK Murder Death Kill. Taken from a game of the same name, this generally means to go all out on your opponent until it is dead.
MMO Massively Multiplayer Online. Typically used as a shortened version of MMORPG but can apply to any online game that supports a large number of players simultaneously.
MMORPG Massively Multiplayer Online Role-Playing Game. An RPG that is played online and supports a large number of players simultaneously.
MOB Mobile OBject. Initially used to describe any character or monster that moves around the landscape, it is most commonly used to describe just monsters now.
MPK Mob Player Kill. Using a mob to kill another player. Usually used when the player killed was not actively seeking PvP.
MP Magic/Mana Points
MT Misstype. Used when a player types into the wrong chat channel.
NPC Non-Player Character. A computer controlled character, can refer to monsters but more commonly used to refer to non-combative characters such as those you talk to and receive quests from.
O7 An emoticon representing a salute. The O is the head, the 7 is the arm/hand.
OFC Of Course
OOM Out Of Magic/Mana
PC Player Character. A player controlled character. Most non-gamers use this to refer to the Personal Computer, while for gamers this has dual meaning depending on the context it is used in.
PK Player Kill. Usually used when the player killed was not actively seeking PvP.
PM Personal Message. The general term for sending a message that only the recipient can see, some games call it a tell or whisper.
PSM Please Send Message (also PST or PSW, see PM)
PT Party. May also be used as shorthand for point(s)
PUG Pick Up Group. A group doing a raid, dungeon, etc. consisting of essentially random people. Compared to grouping with other members of your guild, these types of groups typically have poor communication and a general lack of coordination. Also used to refer to an individual player or players that were picked up to fill in spots of an otherwise completed guild group.
PTT Push To Talk. Refers to a setting within voice communication software (Teamspeak, Ventrilo, Mumble, etc.) which allows your microphone to transmit only when you hold a specific key down.
PvE Player Versus Environment. Fighting computer controlled opponents.
PvP Player Versus Player. Fighting player controlled opponents.
RGR Rodger. Used as acknowledgement of something.
RLH Run Like Hell
QQ Means to cry when typed by itself and used as an emote. Negatively refers to crying or bitching when used to describe another player (“quit QQing”).
RMT Real Money Trade(rs). Refers to the act of selling, or people who sell, in-game currency for real money. Game publishers view RMT activity as illegal and contributing largely to problems with the game economy, they can and routinely do ban accounts of players who either are RMTs themselves or who buy in-game currency from RMTs. The general gaming public views RMT accounts as “lesser players” since they are not really playing the game, and look down upon players who purchase in-game currency from RMTs since they are essentially cheating and not playing the game how it was meant to be played.
WC Water Closet. Initially a term used by Japanese players referring to using the bathroom, its use has been picked up by some English speaking players as well.
WTB Want To Buy
WTS Want To Sell
WTT Want To Trade
WTG Way To Go