I'm sure I've seen 410 in the wild, but it's pretty uncommon. If you're keeping track of things well enough to know that there used to be a page there in order to serve a 410, you're probably keeping track of things well enough to be able to do something better, like redirect to an updated URL.
> Who knew there were so many different status codes.
Note: Everything with a reference that's not RFC 7231 is an extension; don't use that status code unless you actually implement that extension. For example, don't use 401 (Unauthorized) instead of 403 (Forbidden) unless you actually implement the RFC 7235 Authentication extension.
I use it to mark pages that I have taken down for good [1]. I have also used 418 ("I'm a teapot") response code on my gopher server to discourage web bots from attempting to index the site.
Edit--added note
[1] For all the good it does. I just checked my logs and I still see requests for pages I marked as "gone" 15 years ago.
https://en.wikipedia.org/wiki/List_of_HTTP_status_codes#4xx_...
This was famously used by Mark Pilgrim:
https://en.wikipedia.org/wiki/Mark_Pilgrim#%22Disappearance%...