M.K. Pump
You do the M. K. Pump by sticking your arms out like a robot and flexing your biceps. People do it after they do something cool, but it's just for show.
After I beat him in a rap battle, I M. K. Pumped like I was in a commercial.
She flexed like a donkey after she won the game.
He M. K. Pumped so much, his shirt popped off.