-When you can't walk 20ft to the bathroom to take a piss during in a intense match and instead you use your gatorade bottle to piss in.
-You skip out on dates.
-You haven't seen the sun in the past week.
-Your wife calls and you press ignore.
-You constantly say "HEADSHOT" in real life for no reason. (aka fps doug haha)
-You drop out of college because you can't fit in your class schedule with your gaming sessions.
-You rely on caffeine/stimulants to boost your "reaction" shot.
-When you get fired from your job and you scream at your boss, "RAGE KICK MOAR!"
-You haven't taken a bath in the past 4 days. Enough said.
-You take your anger out on someone else in RL when you constantly get pwned in-game.
-You have the constant need to punch your monitor and smash your keyboard. (falls under getting pwned.)
-When your main default gaming keys on your keyboard are dented in with your finger prints.
-When you got a gook of dead skin around the edges of your mouse and keyboard.
Haaa, that's all I can think of at the moment. Feel free to add on.