These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Their pre-Twoism stuff that was leaked mysteriously, and even if it wasn't Boards(Word of God implies they're legit, however), they're pretty awesome.
Tomorrow's Harvest is starting to be considered this by some of the fandom, with its epic, expansive sound inspired by 70s and 80s film scores.
"Roygbiv", their arguable Signature Song, is so well-loved that when Warp Records announced a 20th Anniversary box set, they let the fans choose a the of the songs that would appear in one of the CDs. "Roygbiv" won second place, only suffering by a landslide defeat from the everlasting "Windowlicker".
Magnum Opus: Boards of Canada have three of them: Music Has the Right to Children, Geogaddi and Tomorrow's Harvest. Pick one.
Nightmare Fuel: Parts of Geogaddi (there's also a few normal, soothing ambient tracks in it as well) and the In a Beautiful Place Out in the Country EP
How about the "I... Lovveee... You..." samples on Music Has The Right To Children? Downright Uncanny Valley stuff right here.
And within Geogaddi itself, "You Could Feel the Sky". See below for further info.
Opening The Mouth. My God.
"The Devil Is is in The Details". Not a good idea to listen to in a dark room.
"1969," which crosses Boards of Canada's Right to Children-era sunny sound with unsettling vocoder bits and references to cults.
"All the mystery and magic and all this kind of nonsense that built up around the last record [Geogaddi] got to a point where it was just silly. People were understanding things from our music that we didn't put in there and were saying there was an evil undercurrent to everything. And we are not like that at all. It was a theme that we wanted to pursue on that record but people have understood from that that we always put secret, dark, sinister, and satanic things in our music. And that became more important than the music itself."
Signature Song: "Roygbiv"... not that it's the only one that can be called that: "Dayvan Cowboy," "1969," and "Music Is Math" also are contenders.
What Do You Mean, It Wasn't Made on Drugs?: Although it's not known if Boards of Canada does drugs when composing music, many fans feel that listening to Boards of Canada's trippy, psychedelic sounds is a drug experience in itself.
Especially when on drugs.
There are numerous drug references in the song titles ("Happy Cycling", for instance, is often believed to be referring to Albert Hoffman, the man who discovered LSD and famously went on a bicycle ride under the influence of it). That, of course, does not mean anything about what the band actually does, just that they are likely aware of the frequent comparison between their music and psychedelic drugs