Same here, soldier and duty go hand in hand..even if it is painful.
Technically everyone does, but not everyone's able to 'release' it. It's really just the animal that most represents you. In my case, the hawk is graceful, strong and solitary and yet will fight to the death anyone who goes after her young. She's also aggressive and for food will kill prey the same size as her, but at the same time she only kills if provoked.
Shang Tsung's animal is the cobra, because the cobra is cunning, fast and never wastes an action if he could help it.
I personally think I got the better of the two, but that's just me.