Your sitting alone in what you thought was a safe place, you were bit a few hours ago and your friends left you behind with a handgun and one bullet. You sit there thinking over and over trying to think what you should do, you can feel that your starting to turn but as you start to pull the trigger a zombie bursts into the room, What do you do waste yourself or the zombie?
If it were one of my handguns to decision would be sealed as soon as I started to pull the trigger. I make sure my firearms have a fairly light pull as this helps with accuracy. If I started to squeeze to trigger it would be too late to change my mind as it would be splattered all over the ceiling.
Honestly, I would look around the room, find something to kill the zombie with first. ANYTHING heavy or sharp would work, especially since I'm not at all concerned about being bitten; I'm already infected, so using a pen to stab the zombie through the eye in order to puncture the brain wouldn't be such a bad idea. Then, I would think back on my friends, and wonder why they hadn't shot me themselves in my sleep to keep me from this agony (and keep their firearm, as they'll sure as heck need it!). Then, I kill myself, because in my opinion any true zombie killer would jump at such an easy shot. The zombie practically pulls the trigger for you. Oh wait, it does!