Die Antwoord.
Don't know how it originally came up in my "recommended", But at first I thought that is not her real voice. They must be using some electronic distortion.
Then I checked out their live action vids. I was wrong. Her name is Yolandi Visser and she really sounds incredible.
Most of their music is not suitable to post, songs like "Happy go $ucky #ucky" or "Cookie Thumper" but I found them on Letterman doing a PG rated version of "I fink you freaky"...
https://www.youtube.com/watch?v=rJ214Md00vs