The WoW voice emotes, especially the random /joke and /flirt were amazing. http://www.wowwiki.com/Flirt Guildwars had synchronized dancing.
I would like to see some group emotes.. some for pairs and some for larger groups of maybe up to 4-6 that can be synced up would be cool. Though apart from dancing and flirting I'm at a loss as to what those would be.