[meindnoch]

>Using actual photons in something laser like. The problem here is that your lightsaber would go on forever, photons won't just peter out after a meter or so. So, you would need, well, something to "cap" the lightsaber, both as a cap in terms of ending something, and a cap as in "capture" or possibly even "reflect."

What about using a proton beam, and exploiting the Bragg peak to ionize a finite-length column of air?

[at_a_remove]

Well, protons beat out electrons for at least keeping the divergence down, any volume of lightsaber with a net charge is still going to be vulnerable to fridge magnet attack. Also, I have a strong feeling that it wouldn't look very lightsaber-ish. More like a rapier, although I guess for aesthetic purposes you could have scores of little emissions tubes and switch between them on the order of milliseconds and hope that persistence of vision would create an illusion of thickness.

I have a feeling that the sudden stop could be nasty for even the person holding the hilt, just tons of energy spraying wildly around, a big enough radiation vacation that even the Hulk might blanch at soaking up the gammas. It would still technically qualify as handheld melee arm, but it would be so indiscriminate as to be an inelegant weapon of a more uncivilized age.