"Raynor M'Boy" is a phrase used as a rallying cry for many things, including games and competitive activities. It originated while Stevie played a Starcraft Tower Defense match with Tracy. Stevie put all of his money into Jim Raynor units. Stevie was so proud of his Jim Raynors that he coined the phrase "Raynor M'Boy!". The Jim Raynors led him to victory, or so the story goes. "Raynor M'Boy" is a lot like Stevie's boy H. Jon. Stevie has a lot of boys in his life.
It is appropriate to yell "Raynor M'Boy" while gambling, playing Disc Golf, or any activity that can benefit from Jim's heavy machine gun and power suit armor.