Yay Pete, I kinda stumbled into that one.
Friend came round with a bit of his car suspension with a long bolt well and truly stuck inside forged alloy, everybody had already had a go with hammers, heating it, tried to drill out and finally snapped a hardened pin punch inside it! So we tried anything I'd got and we ended up deciding it was probably scrap. He'd packed it away and we were sitting round talking about other stuff when I thought about using the hammer drill which got it out. We were dancing round like a couple of idiots at our success, I was wondering why I'd never made the connection before.
Maybe I should put it over on hints and tips to make it more visible as it's worked on anything I've found a need since, if you turned up various drift sizes and weld them to old SDS bits you can knock anything out much easier than using a hammer. Last used to get a washing machine drum bearing out for a neighbour which was so tight it was ringing like big Ben.