Time is by far my favorite. Took listening to it as an adult for it to click, as a kid you were there for the music. Some young adults get it the first time though, and the look on their faces when they do...
Nah, the whole album is excellent, but track 3 was what put me on a path beyond my parents' classic rock collection and towards getting into things like Cut Chemist and J Dilla
The Great Gig is gorgeous, but On the Run changed my understanding of what music could be
If you ever see the PF cover band Brit Floyd playing anywhere near you, I highly recommend seeing them. Brought me nearly to tears with how true to the source material it is. For those of us born too late for pink Floyd's heyday, it's damned close enough to the original.
They play the hits and knock them out of the park. The backup singer on Time was so amazing that the audience erupted into standing ovations and cheers like 3 times at the show I saw. And the laser light show was incredible, holy shit.
Just the time signature of "Money" is a work of art. You spend most of your time listening to 4/4 or 3/4 but Money does 5/4 7/4 apparently! in a way you don't even notice
Edit - haven't listened to it in decades but now I think about it, the comments below are correct, it's 7/4 which is even odder