One man comes to mind, I'm intimidated even typing his name: Fabrice Bellard.
He built his own 4G basestation which ran on a PC. He created ffmpeg. He wrote a linux emulator in Javascript. He created his own image format (BPG). These are the tip of the iceberg.
How one man is capable of achieving so much is quite astounding. Here's a quote from the article above:
"If there’s a secret to this superhero-level productivity, it appears to have less to do with comic-book mutation and radioactivity, and far more with discipline, confidence, rigor, and many years of practice."