I wouldn't bother unless it was someone I identified with or cared about.
Considering that I don't agree with majority of the world on various ideas - for fuck's sake, 80% of the world population identify themselves as theists, I'd say screw it. God can save them or some shit.
Running into a burning building to save someone is the dumbest idea. You're not in a Hollywood movie. Smoke inhalation and burn damage is serious business. Let the trained professionals handle it, don't become another fucking casualty. I've been in a rather small fire, and it's not pretty.
The cold sore thing isn't a big deal. It's a different kind of herpes, it's not the same as genital herpes and it can be gotten rid of fairly easily. And I might add that mouth-to-mouth resuscitation, especially by an untrained person, has something less then 2% chance of actually doing anything. It's not the same thing you see on every fucking movie with romantic subplot involved. Either the person would be okay anyways, or you'll have to pretty much break their ribs pushing on their chest in order to make it work. It's that brutal.
For all I care, I'm more important then a stranger. If it meant I stayed alive, I'd kill a stranger, although I can't imagine of such a situation arising in any type of rational reality. I'm not talking about the mugger/attacker type of stranger here, too. Just a regular bystander.
Why? Any type of belief in a soul is downright retarded. This is the only life I've got, and however pointless it might be I'd rather have the ability to experience the world then, well, not. Every ounce of absolute agony is still more fun then non-existence. Although given the fact that you won't really know that you don't exist because you don't exist kind of evens out the whole deal if you think about it.
I can be very egoistic. So no, I wouldn't feel much guilt, if any at all.
Guilt, after all, is just another form of oppression.