RS is an abbreviation for Real Shit. It's a common saying when gangsters talk, or when some of us pretentious fags feel like a hood rat.
TJ: ayyy nigga! you got dat good shit bruh?
RayRay: yea my main man! RS bruh. real shit.
Tyler: Hey boss, did you get that Q3 sales report?
Richard: Yes I did. RS, expect a promotion in a few weeks.