Now, see, actually, steephie's question isn't all that clear.
Does it mean:
1. Would you kill in self-defence, to save your own life, if the person you would kill was clearly the aggressor?
Or does it mean:
2. Would you rather kill or die, in a situation in which you would have to kill an innocent, to save your own life?
For example, imagine you are kidnapped by an evil genius. You awake to find yourself in a water-tight cell. Your cell slowly begins to fill with water - you'll drown if you can't escape. There is a sliding door in one wall, with a button next to it. Pressing the button opens the door and you can escape - BUT if you press the button, it will also set off a cannon, which is aimed at the head of an innocent child in the adjacent cell, visible from yours. The child would certainly die if you press the button.
Would you rather kill, or die?