Nerd: Someone with excess knowledge on a given subject. Generally known to have bad hair, glasses, and laBORatories.
See Also - Scientific Theory of Relativity, Wonka brand candies, Encyclopedias
Geek: Someone with excess knowledge on an obscure subject. Chances are, nine out of ten phrases that come out of their mouth are obscure references.
See Also - Star Wars Canon, Basement Dwellers, Extra Terrestrials
Dork: Someone who is unable to present themselves appropriately in public. Nobody really knows what they look like, because no one ever took the time to pay attention to them.
See Also - Loser, Wimp, Disney Channel Original Movies
Redneck: Someone who has perfected the backwoods style to the point that they no longer fit in with the rest of us. They are usually willing to go hunting in a moment's notice.
See Also - Whitetail Deer, Miners, log cabins
Hillbilly: Unlike a Redneck, a hillbilly is completely ignorant of anything but the bare basics. When visiting the city, often the first thing they'll comment on besides the span-dangle eelectric lights and fancy-shmancy automobiles are indoor outhouses.
See Also - Town Mouse/Country Mouse, Generic 60's Sitcom, Generic Black-and-White Comedy
City Slicker: The counterpart to hillbilly, instead of complete ignorance toward anything but the bare basics, they usually are completely ignorant to anything that is not subject to tax. They usually have an allergic reaction to fresh air and its many forms.
See Also - Town Mouse/Country Mouse, Playboy, Tycoon
The list goes on and on, but there aren't enough witty references left to keep it worth reading.