This works the best when you have 2 or more of the exact same characters (gender and primary class).
Some people try to sync dancing by timing the /dance emote when there is a better way if both your partner and yourself start the dance and you not join the dance. To start dancing at the same time, both people type /dance * and your characters will not do anything for about 5 seconds. After this is up then both characters will start dancing at the same time. This is usefull for those guilds who have like 20 people sycning the same dance all in a row.
Alone with the complete list of in-game commands, here is another one that was not added. Type in /flex into the text box in the game and your character will flex. This looks the coolest for Monks when they do this.