My most inspirational and eye-opening artists would include:
Luigi Russolo
John Cage
Harry Partch
Moondog
Philip Glass
Karlheinz Stockhausen
Edgard Varèse
Raymond Scott (and Bob Moog for that matter)
Delia Derbyshire
Daphne Oram
Terry Riley
La Monte Young
Steve Reich
Pierre Schaeffer
Pierre Henry
Wendy Carlos
Brian Eno
Kraftwerk's first 4 albums (I, II, Ralf & Florian, and Autobahn)
Don Van Vliet
Louis & Bebe Barron
Perrey & Kingsley
Beaver & Krause
Tom Dissevelt and Kid Baltan (Dick Raaymakers)
Morton Subotnick
Harmonia
Popol Vuh
Can
Fred Deakin
Jimmy Cauty & Bill Drummond
Manuel Gottsching
Hans-Joachim Roedelius, Dieter Moebius, and Conny Plank in any of their various incarnations
Klaus Schulze
Karl Hyde
and just about any of the artists mapped on the
Electric Love infographic.