The funnest one off the top of my head is how Yudkowsky used to think that the best thing for altruists to do was build AGI as soon as possible, because that's the quickest way to solve poverty, disease, etc. and achieve a glorious transhuman future. Then he thought more (and talked to Bostrom, I was told) and realized that that's pretty much the exact opposite of what we should be doing. When MIRI was founded its mission was to build AGI as soon as possible.
(Disclaimer: This is the story as I remember it being told, it's entirely possible I'm wrong)
(I use the term "full reversal" to mean going from high confidence in a belief to high confidence in the opposite belief. A "hard reversal" is when a full reversal happens quickly.)
When have you noticed and remembered peers or colleagues changing their minds?
I think the question might need some modifiers to exclude the vast amounts of boring examples. Obviously your question does not evoke answers so boring as "Oh, the store is closed? Okay, then we can't get milk tonight" but what about a corporate executive pivoting his strategy when he hears business-relevant news? By now I am bored of Losing-the-Faith stories, but I don't deny their relevance to human rationality.
Anyway, I think full reversals tend to happen much less frequently than moderate reductions in confidence. Much more common are things of the form "I used to be totally anti-X, but now I see that the reality is a lot more complex and I've become much less certain" or "I used to be completely convinced that Y was true and the deniers were just being silly, but I read a couple decent challenges and now I'm just pretty confused overall". One way in which this happens is when someone accepts that their strong belief actually depends on some fact that they don't know much about.
But to try to directly answer your question, I might list:
One of my friends became polyamorous after initial strong feelings of reluctance when brought up by a partner thanks to arguments on the internet, and now desires it for themself. This is the second most impressive mind change I've witnessed in others (first is private, but think "changed behavior you've been doing for years that you'd think would be blatantly obviously bad to anyone that would've ever been able to change in the first place").
If you cant change your mind, then I struggle to see how you could practice science. You do have some very good scientists "go emeritus" (have stuck priors) late in life, and I wonder whether this is a trap for very good thinkers who have been mostly right all their careers and forget how to be properly skeptical. Is a paper being withdrawn by its authors count as a public change of mind?
Search turns up a few threads on self-reported personal changes of mind. I'm curious here about the third-person perspective: When have you noticed and remembered peers or colleagues changing their minds [about important things]? I'm particularly interested in examples from the group of people who seem to regard a book on how to change your mind as a cultural touchstone, but stories about those whom such people work with and look up to seem likely to also be relevant.