Sparking and glowing, using a huge 7 inch analog meter from an old tube tester. Kinda old school using 555 timers and Op Amps. A lid will fold up giving more display space. Some things I have to install: 4 inch lightning disk, large vacuum tube, glowing voltage regulator tubes, parts for a Jacob's Ladder, etc.
The victims, er, couple will each grab a copper handle and kiss. Sound effects and the meter will respond. As the meter rises past certain points, more things will happen. At some point the handles will vibrate and loud arcing effects will sound.
It can be calibrated for differences in skin resistance by having first one then the other person of the couple hold both handles, adjust for full scale for each, then set the dial halfway in between.