GAK67 has a point, up to a point. He seems to be more concerned with method. Whereas, I think jgoins is talking about will.
I'll say up front that I don't believe that I am an expert at killing or murder or the tools that one might use to accomplish these things, or defending against these things. But I do believe this: "It is better to be able to receive an enemy, than to rely on their likelihood of coming". So, I consider these things.
So, for GAK67:
"To kill somebody with your bare hands takes physical effort and skill" - ...not to mention that there are no sure things. To discuss "bare hands" without knowing who your opponent really is would take too many keystrokes. Anyway, the answer is: That's why you use a tool.
"To kill somebody with a knife you have to get close and use more physical force" - ...I think that you are off the mark here regarding the "force" factor. It sounds to me like you are equating "bare hands" with a knife attack. I don't think that they are. 1st off, your knife should be felt, not seen (unless your goal was induce terror, but that's not what we are talking about). Take your basic prison shiv job. Someone is in the lunch line or walking down a hallway and Pow! Zap! Boom! (Batman reference) you feel 3 punches to your kidney. But, they aren't punches. Once the victim realizes that these are knife wounds they should run away. If the victim is still vulnerable 7 more holes will probably provide enough leaks to get the killing job done. I like the prison hits in the film American Me (1992). As far as "getting close", that's the point (pun intended). Plus, lets not make it sound like these encounters, even "bare hands", are like a boxing match, with rings, gloves and referees. Ambush is an excellent tactic. Take the rash of Knockout Game street attacks that we had in the USA a couple of years back. Not a whole lot of skill there. But a great tactic. My point is that a 'proper' knife attack is effective, while using a lot less calories compared to "bare hands".
"you don't get very many people killed by a car in their house" - ... that's why you don't use the car tool inside the house. Are you saying, for instance just taking you GAK67 as an example, that you are never in an open space? Do not have general habits of going to work, the store, walking around, etc. Just a little research puts a perp's F150 right on your ass (or, over your ass).
"To kill somebody with a bomb takes some education and training to make it in the first place." - ...Yes. But a 5 gallon can of gasoline and a pack of matches will only cost $50 and requires virtually no brains at all to use.

For pulse:
"But it makes it a fucking lot easier to do it with a gun. " - ...not as easy as hopping into an F150 with a 5 gallon can of gasoline packing a 3 inch folding pocket knife. Knife carry laws in the USA vary from state to state. But, you don't need to pass a background check every time you buy one. Or, buy a car, Or, buy gas. Pulse makes it sound like shooting a gun is as easy as hitting the Escape Key. It is not. For the most part, to be effective you still have to get pretty close to your target. Sure, Charlize Theron makes it look easy in the movies.

If there is will to do it there certainly are ways.