Limit it to your one best, as I'm sure we could all list twenty with no problem.
Mine is Aphex Twin's ".215061" from Analogue Bubblebath 3:
http://www.youtube.com/watch?v=HFYOiwH9EgY
http://www.discogs.com/AFX-Analogue-Bubblebath-3/release/28763
Cheers, sneak
"...may well have been the best neo-psychedelic album released in the 1990s. "
The piece is about 10 minutes long. Ravel stated his idea for the piece was taking a theme and trying "to repeat it a number of times on different orchestral levels but without any development."
It's a tune that just fades into the background nicely. I can put it on repeat for a couple hours, and the slow rises and falls in volume keep me in a good rhythm.
http://www.youtube.com/watch?v=B1T8xgHdMEM
Instantly brings me back to age 14 sitting in my room at 3AM programming, chatting on IRC, and taking breaks to play Threewave/NetQuake CTF.
http://www.youtube.com/watch?v=Ltx7_jjv8OE
Takes me back to being 15, not revising for my GCSE's and programming instead. I think I listed to the whole album (Take of your pants and jacket) on loop for about a month straight.
http://itunes.apple.com/be/app/alphamind-alpha-brainwave/id3...
It keeps me really focused for extended periods.
http://soundcloud.com/juan-bass/olivier-weiter-dunlis-origin...