Is Hocus Pocus instrumental?
Lots of contenders. A lot of them from the surf rock genre, such as Walk, Don’t Run by the Ventures, Pipeline by the Chantays, Misirlou by Dick Dale and the Deltones and many, many more.
And a big shout-out to Glen Campbell playing the William Tell Overture on a 12-string guitar. So much fun to watch, especially the last 30 seconds!
Some Australian teens thought it was the US National Anthem. 
(A reference to a scene from a favorite movie, The Dish: https://m.youtube.com/watch?v=zftKpiI6_sI)
This is a fun thread. Many good songs here. Classical Gas is a favorite, and several others that I didn’t know what their titles were (Green Onions, Walk - Don’t Run). Some fun ones not mentioned yet, and maybe they don’t quite rise to the very top, are some played by Herb Alpert and the Tijuana Brass.
Tijuana Taxi
Spanish Flea – made popular by TV’s “The Dating Game”
A Taste of Honey
The Beatles version with lyrics is way more famous than any instrumental.
Maybe I’ve listened to more Herb Alpert than the average person, but I definitely recognize the Alpert song more than the Beatles song. I didn’t even realize those were the same songs until just now. 
OK, I’ve finally gotten around to looking it up. Yeah, I’ve heard “Green Onions”, though I never knew that was its title. But even after having heard it, there are still plenty of other instrumental songs I’ve heard way more often than it. I can’t even tell you what context I would have heard it in.
There’s a long tradition of instros having the name spoken in some way, usually at the end. I say it’s OK.
I don’t want to live in a world where “Yakkity Sax” is only #98.
“Telstar” is nowhere on that list? That was the first one that came to mind.
That’s definitely the most popular instrumental song in Arlen, Texas.
NM
Chuck Mangione. Wow as a teenager of the 1970s his “Geels So Good” was so popular back then – 1978, he and his flugelhorn reached #4 in June with that single. I looked that up.
The Beatles did “A Taste of Honey”? OK, gee, I guess they did – news to me.
Same here, Herb Alpert’s version of A Taste of Honey is very recognizable. The Beatles’, not at all.
Just so you know, that’s not the actual Beatles singing it. The arrangement is relatively close to what’s on “Please Please Me.” It’s really difficult finding original Beatles songs on Youtube these days.
ETA: Actually, reading through the comments, it sounds like this may be the B-side to an early record, but not the album take of the song. But I can’t tell for certain. It doesn’t sound quite like the Beatles to me, but who knows. I expect drag dog could give a relatively definitive answer here.
ETA2: No, my initial instinct was correct. Here is the same version by what apparently is a tribute band called “Zoom Beatles.” I thought for a second I was going crazy when people in the comments were saying that was a Paul McCartney vocal, and I was thinking that it didn’t sound like him at all.
OK thanks. I found a version of “A Taste of Honey” done by The Hollies. It’s weird hearing a version with lyrics. And I much prefer the Herb Alpert version. Still, Eyebrows’s point is made, this isn’t a purely instrumental song.
Percy Faith’s “Holiday for Strings” https://www.youtube.com/watch?v=f2u0BvyDxdM
“Sleigh Ride” by Leroy Anderson is still played a lot at Christmas. It was originally an instrumental, but later lyrics were added.
Other compositions of his were well known.
“Blue Tango” https://www.youtube.com/watch?v=CnHLKM8hQR8
It was the #1 single on Billboard magazine’s Top Hot 100 songs of 1952, America’s number one hit record for five weeks in the spring of 1952, on Billboard’s national singles charts for 38 weeks and in the top 10 for six months.
“The Syncopated Clock” https://www.youtube.com/watch?v=Q6vvkXd9GRw
“Plink, Plank, Plunk” was used as the opening and closing theme of “I’ve Got a Secret” from 1952 to 1961. https://www.youtube.com/watch?v=aGbUT4bgYuw
Apache by the Shadows.
The Vision On Gallery Theme.
Oxygene by Jean-Michel Jarre.
No? Okay then.
I came to sat “Yakkity Sax.” But then I remembered
Baby Elephant Walk