Assuming button is required, the following 101 results were found.
The greatest invention in IThttps://www.joellipman.com/hardware/the-greatest-invention-in-it.html
Behavioral Issues in the Use of Interactive Systems. If you've guessed it, my vote goes for whoever invented the "Undo" button: cross-platform, multi-lingual, future-proof and as everlasting as human error. More? "By [undoing] repeatedly, you can...