I like the idea of bringing back the guillotine. Swift, certain, and with the right prep you can then harvest organs for transplant — something you can’t do with AC current or gas.
But absent a homicide, capital punishment is unlikely. I’d suggest a smaller guillotine, one that starts its drop around the navel and finishes its transit around the upper thigh.
Send the guilty on a one way ocean cruise on the “Millstone/Neck” Liner.