I wouldn't know how to measure a band's "nicheness", so I'm just gonna mention a few bands that barely anyone knows that deserve more recognition:
Dead Calm: A Canadian heavy/thrash metal band, the vocalists voice is incredible, it's baffling to me that they're so obscure, maybe they arrived to the scene too late.
Feff: Nü/Alternative Metal from New York. They sounded like a mix of Godsmack and Metallica, I'm not kidding. I thought they were gonna be huge in 2006. I actually know them because they added me on Hi5 and MySpace back in the day, the last I heard of them is that they renamed themselves to Untappd and then disbanded.
Jonathan Beaudette: A guy who composes orchestral pieces. He doesn't even get 20 monthly listeners, which means Spotify gets to steal what little revenue he would have gotten.
Meliah Rage: Thrash metal from Connecticut. Another case of a band that appeared to late in the scene.
Maybe MySpace was all the friends we made along the way.