Noob Scout
Bonkus Noobus
Newbie Scouts, or Noob Scouts as they are more commonly known, are new players that have not been playing very long. They have little if any non-stock weaponry and tend to run in straight lines. This makes them easy pickings for explosive-bearing classes such as the Soldier or Demoman.
If you have a weapon that has a wide range of shots, they are relatively easy to kill. Do not let them get close, however, as they will spam their bat attacks rapidly. They are cowardly and will often attempt to avoid attack and defense classes, but can get agressive towards classes such as Spy, Sniper, and Medic, as long as they don't have a Jarate or Blutsauger handy, but even then, they aren't very discriminate with support classes as they have little grasp of the concept of stat boosts. They can commonly be found running the same path to the intel over and over again. This makes them an unnecessary distraction to engineers, so do your engie a favor and slaughter that pest.

Rush Scout
Bonkus Saniccus
As their name implies, Rush Scouts will often run straight towards their targets. They are poor at capturing control points, as they have trouble staying still very long. They commonly use items that boost speed or reduce damage. Some known favorites are: The baby-face's blaster, The pretty boy's pocket pistol, The Atomizer, The Sandman, and The Flying Guillotine.
They are willing to take risks, even attacking Heavies paired with medics. If their enemies' intelligence or Australium briefcase has already been taken, they will hide near or even right at the intelligence spawn point until it respawns or is returned, often using the taunt ability or wasting ammo to pass the time. This leaves them open to Pyros or Heavies.
Though dangerous, they are not very loyal, and will gladly switch teams if theirs is losing. They are very unpredictable, making them hard to kill. If you prefer the Heavy class, pair yourself with a medic. This may attract the attention of a Rush Scout, which will make them come close enough to be killed. If they are equipped with speed reducing weapons such as the Baby-Face's Blaster, Snipers can take them out if they react fast enough, but avoid their shots, as it will make them faster and more difficult to catch. Soldiers can easily shoot their feet to slow them down, but this will not work for long. They tend to travel in pairs.

Sly Scout
Bonkus Espionagus
Some scouts choose a different approach. These crafty critters are the result of a Spy that switches classes either for no reason, or to be less restricted speed-wise. The Sly/Spy Scout will hide in the most well-hidden nooks and crannies they can find, using their multiple jump and quickness abilities to hide themselves quickly and in more places than the average spy would be able to access.

They prefer weapons that they can use to take their enemies out quickly with. Some known favorites are: The Sandman, The Wrap Assasin, The Atomizer, The pretty-boy's pocket pistol, Mad Milk, and The Force-A-Nature. They also like to equip themselves with health or attack-stat increasing weapons that focus mainly on speed and damage.

They are not relatively dangerous unless you get close enough for them to kill you. Unfortunately for you, they prefer long-range weapons to shorter ranged weapons. Wide-Range weapon classes or explosive-wielding classes can take them out easily if they discover their hide-outs. Preferred classes are: Heavy, Pyro, Soldier, Demoman, and (occaisionally) Engineer. The heavy's rapid-fire minigun is well equipped to kill these sneaky little Scouts, as well as the Pyro's flamethrower, which makes them easier to spot and hear. They easily fall for traps, as they are often desperate to reach their targets. Sentry guns can root out the Scouts with relative ease. The Demoman simply has to put bombs in a well-known hiding place of theirs and KA-BOOM!

Defender Scout
Bonkus Camperus
The Defender Scout is a rare sight. Often paired with Sentries or Medics, the Defender Scout does exactly what it's name implies. They will stay close to their intel room, and if an enemy gets close enough, they use their speed to distract them until they are either killed by a passing teammate, or are killed by the defender itself.
They are patient, yet easy to distract, if one were to cause a lot of noise nearby, the Defender will come check it out, which can set them up for a trap set by a Demoman. Heavy-Medic pairs, Pyros, and Demomen are the only classes I know that can beat them easily.
The Defender Scouts prefer Damage reducing and Speed boosting items such as Mad Milk, Baby-Face's Blaster, Soda Popper, and Bonk: Atomic Punch. They actually don't pay much attention to their attacking and health much because they are used to having sentries and dispensers nearby helping them.

Trolling Scout
Bonkus Trollus
Trolling Scouts are one of the most common trolls in Team Fortress 2. They will do anything to make the enemy team miserable, and as such, often get kicked. This fact makes them loyal to their own team, and a ruthless enemy to the other.
They will often get some of their biggest powerhouses on their team to make a distraction while they slip over to their target without notice. They may even take briefcases and hide simply to make the enemy panic and spread their forces thinly. Then they will repeatedly capture and deliver the intel cases back and forth until the enemy gets a hold on the situation. They are sneaky but easy to kill, and don't care about what happens to their intel or capture points, preferring to focus on their own target.
Any class with good aim can take out these annoying little trolls.
Brash Scout
Bonkus Narcissus
The well-known Brash Scout is very similar to the Troll Scout, as it likes to prank the enemy team, but on a lesser scale. The Brash Scout is a showoff. They are known to purchase vast quantities of popular items, and as such, stand out from the crowd. Sometimes their expensive gear makes them a target to trolls, as the flashy Brash Scout often has a very bad temper.
They will constantly use their best weapons against weak Noob opponents to make the enemy fear or hate them. Commonly used weapons consist of the following: Boston Basher, Soda Popper, Force-A-Nature, Bonk: Atomic Punch, The Sandman, Fan-o-War, Mad Milk, and several others. They are more close-range specialized than most other scouts and will bully players with a lower skill level than them.
The danger level of the Brash Scout varies depending on the actual player's docileness. Docile players often are more violent in vide-game personalities, and use them to take out anger or frustration, or simply just to brag. Classes that wield explosives as their primary weappon choice will find it difficult, unless properly timed, to kill these quicksters. If the Brash Scout is far away enough, a class such as a Heavy can easily take it out, but at close range, it is likely that said Heavy will barely escape with his life, if at all. They Brash Scout is terrified of Pyros and areas with few exits, such as tunnels (Sawmill), or sewers(Double-cross).

Crazy Legs
Bonkus Spazzicus
Crazy Legs is the name of a long since patched glitch that caused the scout's legs to bend at impossible angles while he runs. The name is also used for Scouts that use their speed much more than necessary.
Crazy Legs are know to only use gear that boosts their speed exponentially. They do not take difficult risks unless necessary. Though not very dangerous to players, they are hard to kill, and one must guard their capture points and intel very carefully and diligently to keep them at bay. They often will not go into an area with sentries, and as such, use their own allies as their unfortunate cannon fodder. They are often incompetent, unloyal, and overly fearful of death. They cannot stay still for very long, and get bored easily. They avoid small spaces with few possible escape points, and are known to fear all attack and defense classes, much like the Noob Scout, but are dangerous if you corner one. If you wish to take one on, just hide a sentry gun or play as a Pyro. Simple as that.

Pro Scout
Bonkus Bonkus
Status: Somewhat Uncommon
"Do you have any idea, ANY idea, who you're dealing with?"
This guy is amazing. 'Nuff said. Their skills levels vary, but they are all excellent. They prefer to wing it, solving problems as they go, instead of planning their attacks. They act this way so that their enemy can be more easily caught off guard. They are similar to the Brash Scout it appearance, but are a lot more mature and are less focused on looking good, and more on being good. They prefer to work alone however, and don't cooperate well with others, so they are easy to single out. But killing them is much easier said than done, and I know from personal experience that they are lethal, and a plague to a Heavy unfortunate enough to not have a pocket Medic.