Computers would be the obvious answer (Electricity is more of a phenomenon, which was discovered and manipulated via other inventions)
Spectroscopy is quite important, particularly Doppler spectroscopy (named after the physicist Christian Doppler who discovered the Doppler effect - the phenomena that the spectroscopic method utilises).
The Doppler effect is where the wavelength of a sound changes because of the movement of an object. This spectroscopic method has helped locate most of the extrasolar planets we have found, and may help us to find more 'earth-like' planets.
Or the Snuggie. It's like an artificial cuddle.