Nick Cave, Pete Steele, Glenn Danzig, Andrew Eldritch.
All reasonably low register
The guy from Stone Temple Pilots, who’s name I can’t think of and I don’t feel like searching for. He sings fairly low.
Scott Weiland
lead singer of stp is scott weiland.
also, although unless you’re from northern virginia or the greater dc metropolitan area, you’ve probably never heard of emmet swimming, but lead singer todd watts is an amazing singer who sings in an amazingly deep register. then again, he can also sing a perfect falsetto when covering “fake plastic trees” by radiohead. def. check them out
Mike Patton of Faith No More and Mr Bungle (and a bunch of other constellations since). Sings in any key possible.
Possibly impossible too.
Warren Zevon
R.E.M. - Michael Stipe sings quite a few lower-register songs.
The Smiths / Morrissey
Echo and the Bunnymen
Joy Division
The Lemonheads / Evan Dando
Elvis Costello, about half the time
David Bowie’s got a solid low-register voice. Not Brad-Roberts low, but pretty low for rock.
Adam Ant gets pretty low in the intro of “Strip”, but also climbs right back up in the same song.
Not rock, but how about Lou Rawls?