Here's a not-so-brief list of some of the short-type, initials, abrieviations, terms, etc of the chatting that goes on in SOF2...
...and even some rank initials:

afk = away from keyboard (i.e. player is idle and not currently playing)
ak = AK74
bc = barrel camper/ briefcase…usually refers to barrel camper
brb = be right back (i.e. "gonna go get something to eat, brb"…etc)
camping = staying in one place and just waiting for the enemy to come to you, instead of looking for the enemy.
case = briefcase
cw = clan war
d/c = disconnect (i.e. "damn, man…I got d/c, but now I’m back!")
dd = don't die!
dl = download (i.e. "I dl-ed this new shit!" …doesn’t really apply to SOF2)
ff = friendly fire (i.e. "ff on?" …"Yes, bitch! Stop shooting me!")
ffs = for f*ck's sake
gg = good game
gj = good job
gl = good luck!
heli = helipad or helicopter
hf = have fun!
hp = health (really stands for health points, but no actual numeric amount of health in SOF2...i.e. "shit! i've got low hp!")
jk = just kidding
lmao = laugh my ass off
lol = laugh out loud
nade = grenade
nick = nickname or screen name
ns = nice shot
nt = nice try
NV = night vision
noob/newb/newbie/nub/n00b = a player that is probably new to the game ‘cause he suck!...lol
omg/omfg = oh my god/oh my f*cking god
pad = helipad
ppl = people
recon = reconnect/reconnector (i.e. "he recon! that punk! kick him!")
rofl = roll on floor laughing
sn = screen name (i.e. the name you use online)
tk = team kill(er)
Thermals = Thermal vision
ty = thank you
w/e = whatever
wth = what the hell?!
wtf = what the f***?!
wtv = whatever

Misc. Ranks
(in order of highest to lowest...although I'm not too sure about which is higher: cpt or sgt?)
LDR = Leader
GEN = General
LT/LTN = Leutenate (sp?)
CPT = Captain
SGT = Seargent
MJR = Major
PVT = Private
CDT = Cadet
...there's more, but even I'm not sure about the rest...