Breakfast Topic: What's okay in a duel?

I can't say I duel much -- at least in part because I primarily play a healing-specced priest who's just hopeless at doing damage -- but also because the informal etiquette of duels confuses the heck out of me. And even worse is that everyone seems to have different opinions of what's appropriate! Some say that a duel is "anything goes" and that both sides may do whatever they can or wish in order to win. Others say that using class-specific abilities is acceptable, and nothing else. (I.e. no buffs from friends, no potions.) Some profession-related items are acceptable (engineering trinkets) while others are not (alchemy potions). In short, the entire affair is sufficiently complicated that I simply steer clear. So to the serious duelers in the audience (you know who you are!) what is and what isn't okay in a duel?

[Fan art by Guillaume Bonnet]