These are the most common abbreviations used when referring to video games.
Genres
FPS
First-person shooter
TPS
Third-person shooter
RPG
Role-playing game
RTS
Real-time strategy
MMORPG
Massively multiplayer online role-playing game
MMOG
Massively multiplayer online game
Game Systems
GB
Game Boy
GBP
Game Boy Pocket
GBC
Game Boy Color
GBA
Game Boy Advance
GBA SP
Game Boy Advance SP
GBM
Game Boy Micro
NDS/DS
Nintendo dual-screen
NES
Nintendo Entertainment System
SNES
Super Nintendo Entertainment System
N64
Nintendo 64
GCN
GameCube
PS
PlayStation
PS2
PlayStation 2
PS3
PlayStation 3
PSP
PlayStation Portable
X360/360
Xbox 360
Companies
SCE
Sony Computer Entertainment
—A: America
—E: Europe
SE
Square Enix [Also be referred to as "Squenix" or "Square"]
Regions
NA
North America
J
Japan
E
Europe
Other
PSN
PlayStation Network
UMD
Universal Media Disc
XBLA
Xbox Live Arcade