Harpies, lamiae, greater gorgons, etc. Other bards, too! Not just any sorcery that has, say, a verbal component. The important distinction about this ability is that it can be done as soon as it happens, regardless of initiative.
That being said, players kill me -- what they complain about. So, the bard can use any weapon, has all these thief skills, casts spells from two schools of sorcery, and has special unique abilities. And yet... this class stinks! I don't get to do what I want! Ha!
HYPERBOREA- A Role-Playing Game of Swords, Sorcery, and Weird Science-Fantasy