Shawns/Joiners are typically insane, ridiculous individuals. They like playing Team Fortress 2, but only if by playing, you mean HAXING. They were some of the first people to use words like "Fail," in real life and they're the only people who can fit the word "Headshot" into any conversation. They also do very good impressions.
You will usually be able to recognize a Shawn/Joiner from across the room by his ability to tell of his latest TF2 adventures for at least 10 minutes at a time, in a variety of voices, primarily using the stereotypical "Spy" accent.
Ash: Did you hear that Shawn kid with a funny accent in the second row talking about "headshot"-ing people? Is he a Russian exchange student?
Alex: No, he's just talking about his latest conquests in TF2.
Rode: Joiner, quit talking about your video games! I need to start class!