[Alneyan]

I guess SP would mean "Super Pretender" in the case of a competitve game; but SC would probably be more accurate, and less confusing here.

Speaking of SC: it stands for Super Combattant, that is any single creature powerful enough to fight on its own (in the early game, it would be any creature able to take Independent provinces without any sort of support, and without breaking a sweat).

RP would be more like "Roleplay" to me, when you are actually your Pretender (or any other unit for this matter). But then, such is the problem with acronyms. A Rainbow Mage (yet another name for them) would be a Pretender with a few picks in several magic paths, if not all of them; its purpose would be to find most sites, forge many items and cast quite a few spells.

And you have the Internet lingo acronyms, such as lol (for lots of laughs, or laughing out loud), IM(H)O (In My (Humble) Opinion), IIRC (If I Recall Correctly), AFAIK/R (As Far As I Know/Recall) or BTW (By The Way). I do not have any lind at hand for one such list of common acronyms though.