It's the ^-key on German keyboards. One of my most important keys in every MMO, usually reserved for one of the important abilities of my classes (taunts for tanks for example, at least before WoW's threat upgrade). In SWTOR it showed the "create a new ticket" window and I couldn't unbind it, neither did I manage to bind a new function to it.
Since everyone has different issues, I'll wave the "bug"-flag on this one