I think both Facebook and Discord do that. I know that the Discord webapp has a big warning along the lines of "copy pasting code here can lead to a compromised account" and then a message about "if you know what you are doing, come work for us".

Many sites do it, but the one I always recall is reddit.

EDIT:

BBC news puts a rather fancy one in the console

Facebook puts a warning about self xss in the console.

I remember discovering the BBC one because that's how I found out you can use CSS to style things in the console.