A few days ago, I was thinking about how to make a lightsabre (we've all done it). I'd read articles about it, of course, and had decided on a particular way that seemed the most plausible. Basically, the blade is telescopic (like a toy lightsabre), and has lots and lots of holes all over it. Plasma is then blasted out of these holes, I presume in a somewhat similar way to a plasma cutter.
Then, as I was thinking about this to myself, the voices in my head misspoke and said "light bulb" instead of "lightsabre." I corrected myself, of course, and carried on thinking. But then, that suddenly gave me an idea! I had accidentally come up with what I believe to be a considerably more plausible and, in fact, possible way of making a real lightsabre.
To put it very simply and quickly, imagine a 3 foot long telescopic soldering iron that heats up to several thousand degrees, rather than just a few hundred. That's my lightsabre.
It's a little bit more complicated than that, but not by much. It would, of course, be heated by a highly powerful electric current (just as a soldering iron is). The blade would be made out of a metal with an incredibly high melting temperature (such as tungsten or perhaps even an alloy if that would be better). Logic dictates that if the blade has a higher melting temperature than anything else, and if it's heated to almost that temperature, then anything it touches will melt.
But if that isn't quite good enough, then you could sort of combine it with the previous way I described. You could have rows of holes all the way up the blade, each row separated by 5 inches or so, and inside the blade (since it will, by necessity, be hollow), you position many small plasma torches at the opening of each hole, at a forward pointing angle. When these are activated, the plasma jets would completely cover the blade.
I'm not an expert, but I'd imagine this would be able to cut through most objects (a computer, a file cabinet, a chair, etc.) with ease.
Yes, it would need a lot of power, (though, unless I'm mistaken, no more than a TIG welder and plasma cutter combined) so you wouldn't be able to carry it around. But as a concept that waits for electrical technology to catch up (Tesla probably would have been able to create a small enough device that produced sufficient electricity, but oh well), I think this is perfectly plausible.
However, as you've probably guessed, I'm not going to actually try to make this. But I may try to make a prototype if my parents ever get a new toaster, so I could use the heating components of the old one.