So, my top favorite is the human male /silly that leads into “Hey, the KING’S BACK!”
My favorite one aside form that would be a macro I made where I did /lick and /moan at target.
I would cast it when people were running past me on the road, and almost 100% of people would stop and turn around when they realized what had happened, it was hilarious to watch in rear camera view.
My favored emote was a guild/group in-joke which was custom generated via “/em” being used.
And probably not a good idea to use in the era of #metoo sadly, probably get banned for using it now.
But /train was pretty good. Favorite thing of all was one of the required Raid addons for TBC which had an easter-egg slash command that raid leaders/assistants could use to play the Benny Hill Theme song on everybody’s computer.