Whisky vinegar.

A Scottish maker ages vinegar in a cask that held Highland Park. Vinegar takes on whatever the wood held before it. Tom Kitchin named it to The Relisher as the Scottish product almost nobody knows about, and he sends people to Royal Mile Whiskies for the bottle. A search of that shop's own catalogue did not turn up a vinegar, so ask at the counter before you cross town for it. Use a few drops where a sherry vinegar would go, over oysters or into the pan after a piece of meat comes out of it.