Theres are many varients and varieties of nerd, collected here is but a small cross-section of them.
The STOCS Nerd
A modern day variant of the STOCS nerd, though still similar in many ways to their ancestors. Note particularly their sloping gait, slack jawed stare and the anti-social aura of superiority which surrounds them. This lesser spotted variant of nerd is generally best avoided, lest you attract their attention.
Except robby, robby isn't a nerd, i mean look how ninja he looks.
These are nerds not considered nerds in the general populous, but none the less, ask them the best way to rush as ct on de_dust2 in CS:S and they will have an answer, they will call 'tacs'.