A couple neighbor kids have been bragging about the fully functional lightsabers they're building and our boys asked me about it and I explained that no reasonable interpretation of existing physics would allow for such a thing and explained why.
HOW TO BUILD A LIGHTSABER THAT WORKS note: 1) reference to very large power supply 2) reference to rocket engine style power supply 3) reference to Mr. Fusion style power supply 4) reference to magnetic interference ie: speaker magnet disrupting plasma field.
The boys of course needed to share that with their friends and the response they got?
"Your dad is dumb. He doesn't know anything."
That hurt the boys feelings pretty bad. Me? I've been called worse by better people, but you have to love the solid belief in fantasy at that age.
I won't discount it completely though, notice I said "existing" physics. If you apply Moore's Law to Lightsaber Construction, we're about 300 years out.
IF there is any reason to build one besides proving it's possible. I mean, a relative handful of clone troopers wiped the galaxy clean of Jedi assisted by a couple Sith. Just because you're packing a lightsaber doesn't make you invincible. Nor does pseudo-mystical power. Even Yoda cowered in self-imposed exile in a dank swamp after confronting one single sith with lightning and teleporting skilz.