Mine would be Sarrah Kerrigan. She's what all ghosts should be. Decent attack (with the same gun o.O; ), and having the same powers as all the other ghosts, this is one female that truly can turn the tides of battle. Also, its quite fun to let her die purposely...just so you can hear her scream.

"You called down the thunder, now reap the whirlwind"
"Im about to overload my aggression inhibitors"

"It says....push any key...er um, which one is the 'any' key?"

"Knowledge is Power. Power--Leads to Corruption. So we all go to school to be Evil!"