FAQ Frequently Asked Question
TLA Three-Letter Acronym
LOA List of Acronyms
AFAICS As Far As I Can See
AFAICT As Far As I Can Tell
AIUI As I Understand It
ISTR I Seem To Recall
RTFM Read The Fucking (Fine) Manual
GIYF Google Is Your Friend
WIYF Wikipedia Is Your Friend
JIYF the Javadocs Is Your Friend
WTF What The ...?
Huh? Huh? ( = "How the heck did you come up with that?")
??? Huh?
IANAL I Am Not A Lawyer
IMO In My Opinion
IMHO In My Humble Opinion
IMNSHO In My Not-So Humble Opinion
FU FollowUp
OTOH On The Other Hand
OTTH On The Third Hand
+1 I concur
-1 I disagree
SSCCE Simple Self-Contained {Correct|Compilable|Confirming} Example
TINSTAAFL There Is No Such Thing As A Free Lunch
.... and many more
The distinction between acronyms and initialisms is not enforced by some of these.
You're expected to be familiar with others like "FUBAR" already.