I don’t know why I didn’t find this among the top 3 google results, so I gave it some thought and the answer is pretty easy:
The minor pentatonic must be the most widely used scale when it comes to soloing and improvisation. There are many methods to learn it, usually involving boxes around the fretboard. I recently discovered a better method.
The minor pentatonic has only 5 notes, and its shape is really simple. It’s just a cross: