Ambient? 
Celer, Mirror and Andrew Chalk, Oöphoi, Mathias Grassow, Thom Brennan are a few of my current favorites. I can’t say for sure that none of their albums have vocal pads or vocals of any kind, but I haven’t heard all of their albums yet but I can’t think of any album by any of them that would have any…
If stoner rock floats your boat Karma to Burn does entirely instrumental stuff, just awesome riffage and low droning walls of guitars.
There’s lots of jazz with no vocals of any kind too. I really love Cecil Taylor’s solo piano albums (free jazz), Indent, Silent Tongues, Garden, Erzulie Maketh Scent, all just simply awesome. I think Spring of Two Blue J’s and Air Above Mountains are instrumental too, and they’re both awesome too
Tim Sparks’ Neshamah and Bill Frisell, Tim Sparks & Marc Ribot - Masada Guitars (both on Tzadik) are absolutely amazing. Mostly acoustic, all solo classical guitar klezmer. The latter might be found listed as a John Zorn album though.
And of course classical, Stravinsky’s The Firebird and The Rite of Spring, Mussorgsky’s Pictures at an exhibition, Erik Satie, Claude Debussy’s Préludes, Images…etc
Yamashita Kazuhito does (IMO) a great job of interpreting The Firebird and Pictures at an exhibition for solo guitar, I recommend finding both.
Raz Mesinai - Resurrections for Goatskin (avant-garde, drumming, awesome)
Tomasz Stanko - Soul of things (jazz),
Drummers of the Societe Absolument Guinin - Voodoo drums (haitian drumming),
Annie Gosfield - Burnt ivory and loose wires (avant-garde/contemporary classical, I’m not 100% sure this doesn’t have any vocals but I don’t think it has).
There’s lots of other stuff that comes to mind but I really can’t remember if it’s all instrumental.