The 1o1 Oscilloscope is a single-channel, 20Msps digital oscilloscope that fits in the palm of your hand. Better yet, its PCB has a footprint of only one square inch - I don't know if that makes it the world's smallest of its class, but it's damn small. It's powered by a PIC32MZ EF microcontroller, using its built-in ADCs in interleaved mode to acquire 20 megasamples per second with a 6-bit resolution. The frontend features hardware variable gain and achieves a bandwidth of 1MHz. We designed this oscilloscope for Hackaday's contest, "The Return of the Square Inch Project", and you can read many more details about the 1o1's design there.
James Rowley (digital design, firmware development)
Mark Omo (analog design)
Kempton Hall (board layout)
The Return of the Square Inch Project - "Runner-up"