It used to be /ran 6 666 at the start of AB, but several (more religious)
people in my guild argued to have it changed. I can dig up the threads on my
guild's board, but they are all members-only so not much use here

.
My guild adopted half of it, 3/333. Heck, I even suggested it for the first
time on one of our raids (I used to be the Main Looter for my guild) and it
kinda stuck for us. No idea of other guilds adopted it at the same time or
it just spread from LE.
/ran 0 100 or /ran 1 100 was rumoured to be bugged, something about refering
to the time you rolled and some people were able to roll high numbers
exlusively by just timing it. I've never been sure if this was actually
possible but enough mistrust was around to shift to other numbers which were
supposed to be more random. No clue why 6/666 was adopted, but I can imagine
it was because of the biblical reference.
--
Arch Convoker Rhand Drago'Magica
officer of Lowland Elites
Antonius Bayle