Probably my favourite is:

Melina Maes, aka 'Ghost-arm Mel'.
She's an exorcist who learned to manipulate one's own spirit to fight a possessing spirit. She lost an arm dealing with a unique and powerful spirit type.

Using her abilities, she learned to manipulate her own spirit to manifest a 'ghost arm' in place of the arm she lost. Several sessions in, she was recruited by the crew to help with some troubles with the Reconciled, and ended up losing an eye too, which she can also replace with a ghostly equivalent.

Some honourable mention though:

The Three Heads
A gang headed by 3 mad scientists inspired by the Think Tank in Fallout NV. They're legitimate geniuses when it comes to inventions, but are absolute morons in every other regard.

Mr. White
A demon who trades in information. He'll hire you to obtain a piece of information, and in return you may ask him for a piece of information. Behind the scene how this works is when you ask him for that information, he goes and makes the same deal with someone else; find this piece of information (that you asked for), in exchange for information when they need it.

And naturally, all this information passes through him.

Delka
Formerly head of a faction called the 'Wandering Souls', before they were effectively wiped out by the crew. She used ouija boards to communicate with a collection of spirits, allowing the faction to communicate securely.

Goth Adler, aka Douglas Goldheart