Git
Git is Blockchain and it's pretty much the only use of the tech I actually see make sense. Most other uses add too much expense where we could just used a trusted ledger. I know people are all about zero trust but the cost benefit of Blockchain doesn't pan out for almost anything. It's not hard to develop cheaper ways to trust an actor, such as laws. Which is how we create trust today. When's the last time your westernized bank stole money from you?
Well, if you remove a commit in the chain it will disrupt the chain. It's a DAG where the next commit requires the previous commit to be unchanged. So Git does use essentially a cryptographic chain.
The thing is we don't care about guessing the next part of the chain, which is where the mining aspect of Blockchain comes into play. So Git does not include validation in it's process. But if someone does modify something in Git I assure you all of the people who have cloned that repository are able to validate a change happened.
Nobody credits Linus with it because signing things was never a novel idea. The part where you're mining the next hash is the interesting part of Blockchain that's not in Git. And that's also the wasteful silly part.