About 95% percent of today's electronics drives on battery and hence the due credit goes to Alessandro Volta for this wonderful invention. Since it is invented in the year 1800, and has become sensation for this invention, I would like to give the title as "Gadget of the year: 1800"
How it works:

We now have two terminals, and the current will flow if we connect them. The reactions in this cell are as follows:
- zinc
- Zn → Zn2+ + 2e-
- sulfuric acid
- 2H+ + 2e- → H2
The copper does not react, functioning as an electrode for the chemical reaction.
However, this cell also has some disadvantages. It is unsafe to handle, as sulfuric acid, even if dilute, is dangerous. Also, the power of the cell diminishes over time because the hydrogen gas is not released, accumulating instead on the surface of the zinc electrode and forming a barrier between the metal and the electrolyte solution.
References: