Ok. Well, truth is that's not entirely true. I suppose it's a matter of semantics. Are you talking about efficiently killing one person? Many? With which type of handgun or round?
For example, if you were looking to kill as many people as you could in say a stadium, would a handgun or a pressure cooker with some ball bearings and gunpowder be more efficient? If you were looking to kill one person, would a rifle, shotgun or handgun be more efficient? With respect to deadly weapons, handguns are not terrible efficient. If you're comparing to handguns to knives or harsh language, handguns are more efficient.
The operator should also be taken into consideration. Most operators of handguns are not sufficiently qualified to make the as efficient or more efficient than other firearms or other methods of killing.
It's all relative and it cannot be accurately stated that handguns are an efficient means of killing.

When a man with a 45 meets a man with a rifle, the man with a pistol is a dead man.

Could I kill one person with a handgun?
Yes. However, as someone who fires a couple thousand rounds a year I'll say that hitting a target that doesn't want to be hit with a handgun at any real distance is a challenge, and with a rifle or shotgun you will do more damage but the distance factors in.
When you say efficient, do you mean one unsuspecting person or do you mean home invasion defense scenarios or do you mean crowd control or do you mean mass execution?
If I wanted to take out as many people as quickly as possible and egress the situation guns would be the least efficient of many choices. If I wanted to kill one person who didn't see it coming a gun is certainly lethal but so would be many other choices making guns equal to other choices.
Home defense? Yeah. A gun is clearly the top choice. Surprise scenarios? You're in a mall and someone starts shooting up the place yeah clearly poison or a knife or napalm isn't the best option.

Saying "is it efficient?" Is a question that cannot be answered without detailed descriptions of the situation you're referring to.

Do guns win wars today? No. Not efficient.
Are the the estates choice for mass homicide? They'll work to some extent, however not as efficient as other options.
A one on one engagement? They will likely end the engagement but depending on the weapon, ammunition, and skill of the operator lethality varies significantly so efficiency is difficult to qualify.

I think threads like this have a higher probability of leading to someone's death than guns do.

The skill of the operator is pointless to argue about, but like any tool or weapon we are obviously talking about someone who is trained to use it. Not Plaxico Burress.

I don't really understand why you keep trying to sprawl the argument into a million directions. I never mentioned a stadium of people and winning wars. "A human being" is pretty specific. You seem focused on handguns. A rifle and a shotgun are guns, which is what the question is. America originally said firearm so go with that if you'd like. We can argue about what the most efficient gun is, but outside of military grade weapons you aren't going to find a more efficient weapon for killing a human being with. It's that simple.

Spada

No you didn't mention a stadium but you didn't specify what you're referring to in a specific question.
It's like asking what the most efficient mode of transportation is. But you don't know where you're going, when you need to get there, how quickly you need to get there or any important details. You can't say cars are the most efficient when there's public trains in a city, or that public trains are efficient when you live in the country and you need to get to a neighboring township.
You've crafted a terrible question.

All of this is wrong.

I specified a human being. That's clearly a singular target. I never asked if it was the most efficient, so your analogy doesn't work. You seem to be hung up on "most efficient" when that was never a part of the question. You're trying to answer something I never asked and then blaming my question for the invalid answer you gave.

All of this is wrong.

I specified a human being. That's clearly a singular target. I never asked if it was the most efficient, so your analogy doesn't work. You seem to be hung up on "most efficient" when that was never a part of the question. You're trying to answer something I never asked and then blaming my question for the invalid answer you gave.

Oh and by the way when you ask a question of efficiency, you're asking a comparative question... efficiency is a question of relevancy. Efficient relative to what?

Ok. A single human being. I'm assuming now you'll tell .even I should have surmised that were talking about a ranged combat of someone aware of the impending attack.
Fine. With enough skill and proper ammunition and we'll placed shots a gun can be efficient. But by these definitions, rat poison is very efficient. You can drop a box in someone's dinner and it's over. A knife is also quite efficient. Can I swipe at someone's throat and kill someone with a knife easily? Yeah, knives can be efficient. I can be efficient with my car. I mean, really there's plenty of weapons that could be defined as efficient if you assume one person, skilled operator, and the opportunity to deliver the blow.

Yes. I have home defense guns.
I believe that as a skilled operator with significant experience across a variety of weapons makes that tool more efficient in my hands than it does, say, my wife's hands who has little experience with weapons and in whose hands at this point the firearm is more dangerous to her than her assailant. That's something you're completely missing as well, and something that I've brought up several times, the sky of the operator is a significant if not the most significant variable in this discussion.

When did Darkside become a nutter?

We're not trying to steal your guns, man. You can admit that it is pretty easy to kill people with guns. If someone said to me...Eric, we need you to kill someone. I'd respond with "please get me a gun."

EVEN as someone less experienced with guns...I know this is my best route.

When did Darkside become a nutter?

We're not trying to steal your guns, man. You can admit that it is pretty easy to kill people with guns. If someone said to me...Eric, we need you to kill someone. I'd respond with "please get me a gun."

EVEN as someone less experienced with guns...I know this is my best route. I'm not trying to fuck around with a howitzer.

Of course it's the most significant, but like I said several times as well it also isn't relevant. You aren't going to blame a tool for someone using it incorrectly. A grill is a pretty efficient way to cook a steak, so I'm not going to say it's not just because some people blow themselves and their food up while grilling.

If you felt unthreatened, you'd easily be able to admit guns are an easy, efficient way of committing murder.

some people blow themselves