Poor Echo. Servant to that cruel (yet sexy)bastard Vincent Nightray. She carries out her orders without complaint, but is still capable of thinking for herself and acting on her own impulses.
-Quick with the knife hidden up her sleeve. Invokes emotion in readers despite being emotionless herself.
-Harboring a split personality, she also has a different form that I will not name, for fear of spoiling it for you.
I think (and hope) Echo has a vital role to play in Pandora Hearts as the story plays out. A dual-natured character like hers could provide some crucial plot twists, and indeed, already has.