Guitar drone is a varied thing. Sometimes it's loud and unsettling, sometimes gentle and airy. All of it is exemplified here, in superb fashion.
"The Zero Universe" is a clear stand out to me, with bowed guitar constantly threatening feedback atop a rumbling base. It eventually yields to acoustic plucking, which eventually devolves in distortion.
Other standouts: Richard Pinhas (!!!), "Suns Corona Hull," "Live at Beast," "Infinite Downfall," and "Divergence," to name a few.