I've recently (five years ago at most I think) started hearing "bien vu" ("good catch, well-spotted", or in a more general sense, "well done") used in the sense of "thanks". The semantical drift kind of makes sense (for instance if you're trying to drive a nail using your bare hand, and I give you a hammer, both "bien vu" and "merci" would work
), but it certainly surprised me the first time I heard it. I have no idea whether it could be a regional thing, but even so it would be a relatively knew usage as far as I know.