This isnt just about the class. This is about the people who play. Everyone has probably experienced this person one time or another. These will be based off of my general experiences. Feel free to adds yours as well.
The Douchebag: This is pretty self explanatory. These are the players that are often times unguilded or in a PvP heavy guild. They boast about their accomplishments constantly, litter trade channel with leetspeak, and generally make an asshat out of themselves. Their natural habitat are battlegrounds, where you can hear their cries of "LOLZ", "KEK", and "ROFL NOOB U GOT PWNED" a mile away. These are the people who are card carrying members of the Greater Internet Dickwad Club. In BGs they will be telling everyone else how they are doing it wrong and should go kill themselves. In raids they tell anyone below then they need to reroll "LOL NUB, I DID MORE DEEPS IN MAH PVP SPEC, LRN TO PLY".
The Disgruntled Former Leader: This is the guy who used to be in a major raiding guild (possibly pre BC). After taking a long break at the begginning of the expansion (he/she was pissed at the gear reset and all the greens replacing their epix), they came back and joined your guild. They immediately butt heads with Guild Leadership and always think they know what is right. They are very good at healing/tanking/DPS, but always seem to have a holier than thou attitude. They respond harshly to any kind of criticism of themselves while dishing out more than enough. After a certain point of gear, they hold the guild hostage by refusing to not go to Raids if he can't gear up his Rogue alt. This person is always online, but never willing to help with anything.
The ZOMG GIRL: Some guilds have their fair share of female players who are very steady and competent. Then some have the ZOMG GIRL!!! She is usually a hunter and is pretty terrible. Most of her time spent in game is talking on vent with the boys who cater to ZOMG boy. They often times have "online" relationships with several of the members of the guild. When this comes to light, several of the boys will leave, or she will. Usually in a guild, she will either be beloved or hated. There is no real middle ground. She acts cutsie wootsie with all of the guys, and immediately gets into defensive mode if another female comes into her territory. May transfer servers often as the drama builds too high.
The Broke Ass: This is usually a person that everyone likes to play with. They attend all raids and spend a lot of time helping lowbies out in instances. Due to these two activities, they rarely have any gold. They are often seen flying around on their regular flying mount that they had to borrow 500 gold for (and paid back in weekly installments of 50 gold over 10 weeks). To them, 1000 gold is a ton, and they would not know what to do with it. They run around with all 16 sot bags because they can not afford to upgrade. While they are broke, they are usually too proud to beg. They are the opposite of......
The Lame Broke Ass: Often times 12 years old. They constantly ask people in guild to borrow gold, but rarely pay it back. They ask for money for everything including respecs, flying, epic flying, repairs. They refuse to do anything that can actually get them some money. Much like the douchebag, you can find him in battleground (yay no repair bills) or jumping around on the fountain and boxes in Stormwinds trade district. This person does not have any professions trained and won't pick them up because it costs money 0_0
The Mother/Father Figure: Generally, they are older than most of the other guildies. They like for everyone to get along and work hard to that end. They may not be the best player, but nobody really minds because they are nice to have around. They will be the first to try and mediate a problem, but are also the people most likely to get their feelings hurt by someone being rude. People who are rude to the Mother/Father Figure beware. They will be defended to the death by the rest of the guild.
The Ninja AFKer: These are the players who seem to be perpetually on. They are always eager to join a Heroic or Raid, but with one problem. They come with RL aggro and dont announce when it happens. Pulled the boss? AFK. Sent a summon? AFK. Asked a question? AFK. They try to hide it sometimes by putting their toon on follow. When not distracted, they are a nice compliment to groups, but can often turn 2 hour raids into 3 hour ones.
The Meter Linker: We all know this one (and probably have been guilty of it from time to time). They link any meter that shows them on top. This can be and kind of meter. It is used only for the purpose of showing off their awesome sauce. "Oh look, I dispelled 43 times and the next closest was 18", or "WOW 5K DPS OMG" after casting seed of corruption non stop on a pile of spiders in Naxx. They annoy you to no end, and never cease to pull up a meter even when they are asked to stop.
Feel free to post some more archetypes and I will add them to my post. They can be funny or serious. There are more kinds of players out there than I can write down on my own.