When someone or something is so good in useful or effectiveness, they can take on the opps with ease. Being nicknamed the or a Opp Killa.
*picks up peter griffins shotgun*
Oh shoot, got a Opp Killa for this game.
When you see the behind of a woman, so you have no choice but to yell Gyatt.
*guy walking behind girl*
Guy: oh Gyatt! Oh gyaaattt gyat gyat gyat gyat gyattt!!