All great songs- my first thought was Layla as well…
But what about songs that are counted in to start? sorry at work so cant link, but actually I suck at it 
Wooly Bully
Hey- Ya
How could we forget Come Together?
Good Thing, FYC
Yeah NVME702-redux, from the moment Sam says Uno!, I know what song I’m listening to, and that I must “watch it”.*
And yeah, Leaffan, it’s funny. Most of the songs from the era of recorded music that are regularly played on the radio, I can recognize from their first 4 notes (or chords, if you’re being pedantic). Part of it is the production, the sound and EQ of those first 4 notes. Those all give me clues as to what the song is in the case of famous recordings. I can recognize 95% of rock radio playlists from the last 40 years within a bar. Most of our memorable songs have good openings, otherwise we’d have spun the dial, skipped ahead, or whatever was the method for getting new music through the media.
For example, while spinning the dial through a slew of things I already knew I didn’t like on a road trip, I happened onto the very beginning of this. It’s just a fairly generic beat. But I knew it’s sound and the crowd noise behind it and knew I liked it, even if I couldn’t put a name to it, so I should leave it there.
So, who’s up for a thread of songs that start forgettably, but pay off in the end? 
*Apropos of nothing: I love that this man, and by extension his song, are from Dallas. If there was any justice in the world, it would the be the city’s theme song. Barely a rhyme, very little reason; just craziness that somehow works.
He’s also the least douchebaggy person on the board.
For all those who named the opening chord of “Hard Day’s Night” (good choice), this link is fascinating. (it was posted on the George Martin RIP thread).
Very techno-geeky breakdown of the chord.
It turns out to be 3 different chords on 3 instruments: 12-string electric, 6-string acoustic, and piano. And a bass note.
Gangnam Style
The airplane noise at the beginning of “Back in the USSR”.
Also the pumpy organy thing at the beginning of “California Girls” (Beach Boys).
I think this thread proves that there are at least 1000 songs tied for the most recognized into.
And, to contribute to the thread, here’s “Master of Puppets”.
Both versions of Free Bird…
The studio version where you can close your eyes and see Michael, Terry, and Buddy strutting down the aisle to the ring…
The live version that isn’t really also known as Oak’s Anthem, but should be.
Ah, I see - I didn’t realise he was referring to his own kids.
oops - sorry, Pulylkamell
What the fuck are you talking about? I admitted I made an error due to a newborn in the house and said “tom” instead of “hi hat”? Am I missing something here?
ETA: Sorry…I didn’t see the post directly above mine as I was responding as I was catching up to the rest of the thread. No hard feelings on my part. 
Oh, and if you have kids that match my situation, best wishes, too!
Yes, thank you. I’ve sung along with it many times, because I don’t know the words to Mendelssohn.
I offer another close your eyes and click selection. For any naysayer, we can at least shout to it.
I just spent … too long… listening to different versions of this song
Here’s the canonical version, live.
Once you hear it you will understand why multiple versions kept me up way too late.
Agreed. If you are looking for a reasonable person to geek out about music with, pulykamell is your guy.
He’s a pirate from Pirates of the Caribbean
More classical music recognizable intros (that I don’t think have been mentioned yet): (titles in spoiler box for those who want to play “close your eyes and click”):
1. Mozart, “Eine Kleine Nachtmusik”
2. Beethoven, 5th Symphony
3. Grieg, Piano Concerto
4. Vivaldi, “Spring” (first of The Four Seasons)
5. Mendelssohnm 4th (“Italian”) Symphony
Aw, shucks, you guys are making me blush.
No need to get douchey about things.
Late to the party, as usual…
In the “I can Name That Tune in one note” catagory, gotta agree with A Hard Days Night in the Rock/Pop catagory. “Unique” by every definition of the word.
In Classical, I second Thudlow Boink’s first choice
And even though this one might take three notes, you can never have too much of the Beatles:
I Want To Hold Your Hand (2013 Remaster) - YouTube.