

My favorite is Barry Marshall. He thought there was a connection between bacteria and ulcers, which was an unpopular opinion at the time. So he intentionally drank the offending bacteria, got sick as expected, and then people believed him.
More here, including (which I didn’t know until now) cardiac catheterization.
I’m sure better sources exist but https://www.discovermagazine.com/health/these-five-doctors-experimented-on-themselves-and-made-big-breakthroughs
I think that there is 1 current version of Windows, 1 “almost current”, and 1
(I have used Linux for the last 20+ years, and it’s definitely my preferred setup.)