Bands that have never changed lineup?

They had a different drummer at first, but all their recorded material may be with the same four guys. Not sure.

They had a different bass player as well, Lennons best mate. But they kicked him out because he couldn't play and McCartney took over. All their recorded material was with John, Paul, George & Ringo though.
 
Nine Inch Nails. They've had a billion session musicians, but only one real member. Ministry could fit that categorey, too, but then so could Megadeth.
 
Listen to the song Crossfire. It's pretty obvious there is a keyboard player
That song rules.
Session musician, though...

Velvet Revolver was never good. Why would anyone buy one of their albums?
.
Audioslave worked, but for some reason Velvet Revolver just doesn't...


Anyhow...
One man bands...
Bathory - Quorthon wrote all the music, so while there were at one point 2 other members, they were basically just session musicians.
Quorthon - Quorthon actually played everything here, so it was completely him.

2 man bands such as Immortal, I guess...