I use the term "Best" loosely.
Either the funniest, most calming, supportive, weirdest.

I think mine was when I told one of my friends before she heard it from somebody else. We'd discussed it before in a "well I used to do it, but now I don't" kind of way but now I actually had to admit that it was still an ongoing thing for me.
Her words:
"F****** EMO GYPSY!"
She didn't mean it in an offensive way. She was the kind of person who'd say something like that in a moment like that to diffuse tension and because she didn't know what else to say. I laughed because I wasn't into all that "touchy feely, I'm here for you" stuff that everybody and their brother comes out with.

So what was the best response you've ever heard to somebody finding out that you self harm, no matter how they found out.