"Echoes" is the greatest song written. The reprise and the release, the band jam with the two guitar solos in a row, the whale song. Just unbelievable.
Hell, even the intro. Just hearing the empty, ethereal ping...ping... leading into the main theme, you know you're in for something truly epic. The fact that Floyd created such an atmosphere with a single repeated note is proof of their greatness. (Especially Wright's greatness, as he came up with the intro. He wasn't as visible as Waters or Gilmour, but his contributions were nonetheless vital.)
Especially the live version from Pulse. The guitar solo almost hurts, and the light show isn't exactly a detractor.
Sitting down and listening to a Pink Floyd album from start to finish almost always counts as Awesome Music. Wish You Were Here, Dark Side of the Moon, and Meddle are particularly well put together. The Wall is awesome in its own way too, as is Animals. Some may find The Final Cut fits into this category.
Quite a few tracks off The Division Bell. "High Hopes" (music video) is mesmerisingly beautiful, and "Poles Apart" and "Coming Back to Life" are awesome too. There's so much emotion in some of these songs that it hurts, and this album should never be overlooked.
For fans of Floyd's early period, there's The Piper At The Gates Of Dawn. 42 minutes of prime space rock/psychedelia, including "Astronomy Domine", "Lucifer Sam", "Take Up Thy Stethoscope And Walk", "Interstellar Overdrive" and "Bike". Not to mention the singles, "Arnold Layne" and "See Emily Play", that were spawned during this period.
The initial appearance of the four-note guitar motif in "Shine on You Crazy Diamond".
All of "Shine On You Crazy Diamond", more like. Especially when it goes "SHIiINE ON YOU CRAAAAAZY DIiIiAmond"
The section of "Learning to Fly" from "Above to the planet on a wing and a prayer..." to the song's end.
"One of These Days", anyone? The bass line is simple yet haunting, and the slide guitar jam in the second half is icing on the cake. This is the reason why Meddle is a great album.
Even more awesome is the Ascended Meme of playing the Doctor Who theme halfway through it, something which began on the "Delicate Sound of Thunder" tours. So awesome that every tribute act, including and especially the Australian Pink Floyd Show, does it.
"Another Brick in the Wall (Part II)" will always kick major ass. ALWAYS.
At exactly the 2:49 mark is one the most amazing note bends in musical history. Just that 5 seconds there is one the finest moments in music.
If you had to narrow it down to one album, it'd be Dark Side of the Moon, their most critically acclaimed and commercially successful work. It was on the Billboard Top 200 for fifteen years and would have re-entered the chart again had Billboard not changed the rules to prevent that (instead, it remains a mainstay of their "Catalog" chart). When they changed their rules in 2009 to allow catalog albums and re-entries into the Billboard Top 200, Dark Side of the Moon re-entered the chart a few weeks later and has popped in here and there ever since.