"Get Out Of Here Stalker!"

Origin

This meme originated in the 2007 game “S.T.A.L.K.E.R – Shadow Of Chernobyl”, where every time a player passed near or try to interact with a certain NPC (a guard of the “Duty” faction) the guard would say “Get out of here, Stalker!”, which would be his only line, and at times he would repeat the phrase a few times very quickly.(The area in which the NPC was located was a rather major area of the game, so players would pass there many times, and the guard would repeat the phrase almost every time.)

The original NPC-

Spread

The exact origin of where the phrase started spreading from and gaining it’s popularity is uncertain, though it is safe to assume it has been one of the few S.T.A.L.K.E.R dedicated forums such as GSC’s official forums, the S.T.A.L.K.E.R series subforum on Steam forums, or even in general gaming-dedicated forums where fellow STALKERS would greet one another with said phrase.

Use

As well as being used as a sign of recognition among S.T.A.L.K.E.R fans, it is also used as a caption pictures and videos.(usualy, but not limited to S.T.A.L.K.E.R related, or Russia/ Ukraine related)

Here (warning, 4chanarchive- NSFW content) is an example of in a seemingly unrelated discussion. Another one here. (Although discussion is slightly related to the setting of the game, the topic of discussion is not game-related, yet the phrase is used even here.) And yet another one, in an unrelated thread.
In fact, a simple search on the archive would provide quite a few results showing the use of said phrase, in many topics, unrelated to S.T.A.L.K.E.R or gaming even.While the forum 4Chan may be completely unrelated to S.T.A.L.K.E.R, the frequent use of meme’s by it’s users makes it good proof of the phrase’s notability.
Note “Get Out Of Here S.T.A.L.K.E.R” in Encylcopedia Dramatica’s list of /k/ meme’s.
Also, here’s a “Get Out Of Here Stalker” YTMND loop.

Another one with the NPC-

300 remix-

Yet another one showing the NPC-

Used in a Team Fortress 2 related video-

Weaboo Edition