I would guess most dopers could correctly identify the Beatles tune “A Hard Day’s Night” hearing no more than the first chord. I know I can. Are there any other songs you feel confident you could identify hearing only the first note (or chord)?
Layla by Eric Clapton
Hell’s Bells by AC/DC. The opening gong gives it away.
(yes, I know the timbre is different, but you have to remember which is which)
I could probably give you “Painkiller” by Judas Priest, either by the very first drum hit, or the guitar slide after the intro.
Stones’ version of Honky Tonk Woman, of course. “Clank…” “Got it.”
“A Whiter Shade of Pale.”
If we’re using the actual recordings, yeah. I can do this with dozens, of songs, possibly hundreds. There’s so much more information than the actual note. The first two that come to mind are The Nazz’ “Open My Eyes” and Dick Dale’s “Misiorlu”*
Now, if someone’s covering the song (such as the orchestra used to do on the game show we’re referencing), that’s harder. If I don’t have the timbre of the original instrument and the production of the original recording as hints, my accuracy is going to go way down.
*Which is started with a single note, not like the cheaters naming songs that start with chords. Chords are at least three notes, people! 
Came in here to say just that.
“The Spirit of Radio” from Rush has a unique opening.
Sounds about right. I flash on whole songs based on a millisecond flip-past on the radio (yes, I’m old and listen to the radio).
“Lola” by the Kinks.
My Girl, The Temptations
Soul Man, Sam and Dave (well, it’s a slide)
Pink Floyd’s Echoes.
PING!
No music man am I but Rhapsody in Blue starts off pretty memorably. I don’t know if that’s technically one note though.
I’d also be able to name several REM songs, Driver 8 being the easiest.
Good one.
Stranglehold by Ted Nugent
Oh yeah, I’m still an avid radio listener, and spin the dial like mad. My mom used to be surprised that I could recognize a song from such a short snippet. I suspect she could do the same thing, but just wasn’t familiar with the songs.
I was at a college choir/band concert once where one of the songs was “Oronoco Flow” (most famously recorded by Enya). I recognized it on the first chord.
Sure. First note: Same band, same year. I Feel Fine
Edit: First chord: Greig Piano Concerto in A minor.
I think most people have more of these than they might think.
For me, off the top of my head:
Barney Miller opening
Beatles - Day Tripper, Revolution, Helter Skelter, and those previously mentioned
Beach Boys - Good Vibrations
The Band - The Weight, The Night They Drove Old Dixie Down
And those are just the Bs.
mmm
There are a few live recordings that I can recognize by the crowd sound before the music even starts. Such as Frampton’s Baby I Love Your Way. I think I may have heard them a few too many times.