It's difficult to say right now, as I'm not in an actual life-or-death situation, but I'd like to think that I would willingly give my life for my family, friends, random strangers in trouble, the Union, Britain, harmony and freedom in general, my faith, the prevention of evil acts, or to prevent violating any of my principles.
For example, if I was put in a situation where I had to decide between my own life or someone else's, I really hope I'll choose to save the other person.
Once I was asked my a friend whether I would rather steal a large portion of money for some anonymous party, or be killed. I was surprised how shocking it was for some people that I choose death instead. Apparently self-sacrifice isn't held as a virtue by some.