few more shorties starting with letter R

R
R - Are
RMB - Ring my Bell
ROTFL - Roll on the floor laughing
RU? - Are you?
RUOK? - Are you Ok?

few more shorties starting with letter P & Q

PCM - Please call me
PPL - People

QT - Cutie

few more shorties starting with letter O

O
O4U - only for you
OIC - Oh, I see.
OTOH - On the other hand

few more shorties starting with letter N

NA - No access
NC - No comment
NE - Any
NE1 - Anyone
No1 - No-One
NWO - No way out

few more shorties starting with letter M

M$ULkeCrZ - Miss you like Crazy!
M8 - mate
MC - merry Christmas
MGB - May God Bless
Mob - Mobile
MYOB - Mind your own Business