Short for "Oh my God! What the fuck? John Fitzgerald Kennedy Barbecue!". This was first uttered on November 23rd, 1963 just one day after President Kennedy was assassinated in the dialogue below.
(During the cremation of JFK's corpse, 2 random guys walk onto the scene, soon to utter the first OMGWTFJFKBBQ ever)
Random dude 1: OMG!
Random dude 2: WTF?
Jackie Onassis: JFKBBQ!!!!!!!!!11!!!!!!2!!!!!!!!7!!!!!!
An expression of extreme excitement. Literally means "Oh My God, What The Fuck, PoWNeD". With powned being an expression derived from "owned". This expression is often used in the world of gaming.
Guy1: Dude, I just sniped some n00bs head from like 500 yards away.
Guy2: OMGWTFPWND! XD
Dude, remember when Seth was all fucked up at that Mexican Restaurant at the Great Lakes Fly-In, and he decided to yell, "TO DON'S DAUGHTER!!". OMGWTFD!