-When you watch Dawn of the Dead you have the distinct urge to yell "Noobs" because they aren't dealing with Tanks, Witches, and Hunters
-when you wish Bill was your real life friend. Bill's awesome.
-When you are in Times Square and bored, you play the "Who would be my fellow Survivors" (scan the crowd for people who look like they'd be good Zoeys, Bills and Francis) Game. Of course I'm always Louis.
-When you shy away from wearing a white button down shirt and red tie because you'd be "Tempting fate".
You can tell your friends play Left 4 Dead way too often when:
-They constantly look at you and offer you pills. Yeah, screw you too, guys.