Any nice examples? 
There's this transaction where somebody clearly made a mistake. The fee was 291BTC, meaning 136k USD at that day, now worth more than 3M USD and I think that it was not refunded. Some of the story is here.
I'd never heard about this one before. That's really quite absurd. I'm not sure how the person that did it could not have read the news that they would refund him? I can't think of any reason why they wouldn't want a refund because it has to be a mistake. Imagine if that was the one block that some random lucky guy hit instead of a big mining pool
