1. Not claiming corpses. Seriously, I don't know why this one bugs me so much. Hey, free gold, ointments and more for me many times, but it still bugs me.
2. Catfishing other players with your gender. 'Nuff said.
3. Waiting around for the champ boss instead of killing the spawn.
4. Waiting around with your 5 pets for the champ boss instead of killing the spawn (Yes, this deserves two lines).
5. Not having a sense of humor in world chat. You should have to pass a high horse check of some sort prior to turning on world chat.
6. Advertising an item as for sale, but refusing to tell anyone the price. We are not gypsies...well...most of us aren't...
1) agreed, but hey, their loss, your gain!
2) This is a tough one. Since it's a role-playing game, i have no issues with someone playing a male, female, or other persona. The only time I think it could become an issue, is if one party tries to take things outside the game, and the other one has no interest in that. Remember, you are interacting with the character, not the person unless both parties agree otherwise. I have friends who play opposite genders in the game, and when addressing them in game, i always refer to them as their characters gender while in game, or game related forums/team speak etc.
3) Not a lot to be done here unfortunately

It is annoying though.
4) most people don't realize once the boss is out, its a lot easier for everyone involved to NOT use pets. grab a yumi, enemy of one, and armor pierce. Will nab you a power scroll just about every single time. (Maybe different with the new way champs are done). Plus you get the added benefit being able to encircle the boss and have him bounce between you all, instead of running away in a singular direction from the pets, while everyone chases after them.
5) Meh. Its world chat. You have to take the good with the bad, or turn it off

Or ignore certain people who annoy you. ie: the ones lacking said sense of humor.
6) Another tough one. There's a couple ways of looking at it though. First, someone could just be trying to figure out what something is worth, or get the best price possible. If i advertise XYZ for 1 mil, first person gets it. Or that's how it should be. If I ask for an offer, 3 people could PM me, and then I get a choice (obviously for the highest bidder). If i wanted a store front, and set price, I'd put it on a vendor

First come, first serve. When I ask for offers, that's exactly what I want. Hopefully several interested people.
The only thing annoying about Druids at champs is when they cast trees on the alter, ugh brutal. Other than that I can't possibly see what there is to be annoyed about. They keep Newbs alive even.
It's just the most efficient place to cast them. I rock lure stone with my trees, so its pulling everything from everywhere to a central location for everyone. (with restrictions depending on which champ ie: doom/terra/fire/etc). I also have my attacker on to whirlwind. Join in the fun. No druid book you say? Use the mana regen and throw out some area affect earthquakes, or whirlwinds of your own. I actually hit 120 magery from doing earthquakes at champs using other peoples trees.
One of my pet peeves while champing is people not using the restorative soil I throw on the ground to rez them. I don't know if they just don't know what it is, or can't see it, or what. I just find it easier to target the ground when my script(s) are running. Usually they are running around trying to be noticed, so when I go to click, they moved out of range, or thought i was taking too long, or I dunno!
Look for the dirt folks! It saves lives!