The equivalent argument would be banning something that makes murder really really easy without much training or willpower. Killing with a knife is hard, and just not very accessible (if you doubt me, try going hunting for deer with a knife instead of a rifle). The equivalent would be some device that made killing really easy, eg something that supported point and shoot. Like, if someone invented a ray gun that you could just point at people and they would die, that would banned really quickly even by the most libertarian governments (because society doesn’t survive very long with them around, or society doesn’t ban them and is just replaced by another society that does).

Lock picks at least take some skill, they aren’t super accessible. But an RF repeater seems to be fairly accessible according to how quickly it spread (although most modern fobs stop transmitting when stationary, so these are only effective for people who carry fobs in their pockets all the time).

Like power tools ?

They make opening a locked doors very easy.

Or regular non ray guns ? They make killing super easy. And you definitly don't need those for most people.

But oil as well, I mean it makes arson so easy and you can burn entire houses with people inside.

You need to think about accessibility more! All of your other techniques just aren't that effective, which is why they aren't used for much murder very much. Burning a school down vs a gun to rack up mass casualties? The fire alarm would go off and that is that. The same with using a power tool like a drill to kill someone, you can do it if you try really hard, but your chances of success aren't very high.

Anything that makes the deed "easy" is simply going to make it easier to perform and hence performed more often. It isn't rocket science, and it isn't binary! Yes, you can kill someone with your bare hands, or use an ice pick, or whatever, but not easily, like you could with a gun.