The word is best used, however, to describe enemies who must be eliminated in videogames.
You (advising me): There's one to your right...
Me: Oh shit, I'm dead. These gonks just didn't stop. Fucking gonks.
In the movie Lock Stock and Two smoking barrels, the character Hatchet Harry, beats a man, suspected of stealing, to death with what happened to be at hand. Harry, also a porn shop owner, happened to grab a big black rubber cock.
This term arose due to the unwieldlyness of the lengthy phrase "He was beaten to death with a large black rubber cock..." and was shortened to simply, "He got gonked."
If these guys keep pissing us off like this, I'm gonna gonk them.
"what an amazing gonkathon that was you gonking gonkhead... now suck my gonk"
You - (Backhanding the guy becide you) "GONK!"
Other Guy - "Aww fuck. What the hell was that for?"
"I gonked that other guy the other day."
"Lets have a truce. No gonking eachother."