I'm sure other people probably know this by now seeing as I just barely got to level 110, but if you go near Sylvanas in the Undercity as a marksman hunter and have her family heirloom artifact weapon equiped she does a little RP. Part of unlocking a hidden appearance?
***SPOILER***
Lady Sylvanas Windrunner says: Thas'dorah... I have not seen it in years! That's a Windrunner family heirloom you have slung across your back.
Lady Sylvanas Windrunner says: My mother passed it down to my eldest sister. May it bring you better fortune than it did her.
Lady Sylvanas Windrunner says: Remember, Lastgun, that Thas'dorah represents my family's legacy... MY legacy. The deeds you perform while wielding it reflect upon me.
Lady Sylvanas Windrunner says: It is fitting that the bow be in the hands of so skilled a marksman. I trust you will remain worthy of it. Do not disappoint me.