Poor hygiene - greasy unwashed hair that never gets combed - games are more important to the individual, how ever some do actually look after their appearance.
Blunt personality - they are usually in "cuckoo land" dreaming of being inside a video game or what they are going to play when they get home from work/school. Long hours in front of the computer and having no social life leads to an underdeveloped personality, they are generally self-centered and over confident in decisions they make making them look like an idiot out in the real world.
Unintelligent - because of the long hours they spend at the computer they know how to do nothing else only click a mouse button and tap keys on a keyboard, ask them to start a lawnmower(they probably don't know how).
Over reacting - this is usually more prominent in the gamer who is also obsessed with anime, acting out expressions in real life that you would only find in a cartoon.
Under slept - long hours at the computer causes severe sleep debt over time, they can be found to have very pale and badly complexioned skin with raw looking eyes, ignorance to lack of sleep can cause insanity in time.