BoC
When I was still in high school I didin't know anyone that was into electronic music. I accidentally downloaded a BoC track from a file sharing program, and when I played it I was blown away."In the Annexe" was the track, and it introduced me to IDM (and electronic music as a whole). It sounds very downtrodden and melancholy. The first time I listened, it made me feel feelings that no other music had done in my life. When I listen to it now, my mind takes me back to that humid summer night. Since then I've grown to love many genres of electronic music, but Boards of Canada has a special place in my heart. I had been listening to them less since no new albums had been released for ever 5 years. Since they released Tomorrow's Harvest last year, I am back to my old listening habits.
And if you like Boards of Canada, try Casino Versus Japan. Ambient droney IDM, but much less depressing than BoC.