Pros are the opposite of noobs. Pros pwn noobs like it's their job, and in some senses it is. Then they are 'The Pro Shit'... Can also be used to mean that something is cool, or something that pros do ritualistically. I, for example, eat Nachos BellGrande from Taco Bell, because it makes me Pro as hell at any FPS I play.
"No way! He knifed me? He's The Pro Shit"
"Nachos BellGrande is the Pro Meal"
"Betcha little n00bass didn't know I was The Pro Shit"