bought a Wish You Were Here cassette brand new in 5th grade, and played the wheels off of it by 9th grade. That is likely my #1.
Dark Side however, there is no denying its magic. That and Delicate were huge, huge for me.
Animals however, I did not hear until a little later. closer to maybe 10th or 11th grade or so. Animals was released the year I was born, 1977. The first time I heard the record (CD), from the first note, of each song- it sounded extremely familiar, and comforting in some way. I can only speculate a baby sitter, or some other very early experience involved that record, with regularity, during my earliest days. Way cool.
Speaking of baby sitters, this is a great story. I have a friend, Matt, born February 1974. His older sister was responsible for him one night in late February 1980, he had just turned 6. His sister got invited to the Wall show at Nassau Coliseum, and she could only go if she brought 6 y/o Matt with them- and that is exactly what she did! Matt also went to Momentary/Delicate at Nassau in 87 or 88, and the Division Bell/Pulse in 94 (plus tons of Waters shows Pros and Cons etc) so he saw the Wall when he was 6, and 3 Floyd tours in all. for being born in 74, that is pretty solid!
I went to the Division Bell at Yankee Stadium. insane for sure. Bunch of Waters shows over the years. Gilmour once at Radio City, On an Island tour with Crosby and Nash (and Rick Wright).
Meddle, Final Cut and the Syd stuff are great too. Between Syd and Meddle those few albums are not my favorite