An ion thruster is a form of spacecraft propulsion that uses high voltages of electricity to accelerate gas at high velocity. Ion propulsion was used on the New Horizons spacecraft, which took the first ever close up photos of pluto. An ion thruster was chosen for New Horizons because ion propulsion is very fuel efficient. Unfortunately, it's also not very powerful, so ion propulsion is only practical in space for either very small or very long-term maneuvers.
It's turns out it's really quite easy to make an ion thruster; all I needed was a high voltage source (a neon sign transformer), a rectifier (which transforms AC electricity into DC), and a few copper pipes and nails. And the transformer and rectifier aren't even really part of the thruster; they just supply the power.
