Jacob's Ladder
I'm planning to build my own soon, and while looking, I found some inspiration videos:
Double Helix Ladder 15,000 volts:
https://www.youtube.com/watch?v=-AsaGgb5ixo
Ok, how about 200,000 volts?
https://www.youtube.com/watch?v=Jzy_bPnt1_A
This one is safe! So, kid friendly even if it is not a real Jacob's Ladder:
http://hackaday.com/2010/12/12/jacobs-ladder-using-el-wire/