IMMS
I miss my SLX. 
IIRC - if i recall correctly
YM - your mom (i think i just made that one up)
IBTL - In Before The Lock
IB4(anything) - In Before (anything). for example: IB4NewmanMentionsPenises
gg - good game
WTF? = wanna to fuck?
ttt = to the top
TTYL
TLA - three letter abbreviation