There is no song titled Dark Side of the Moon on Dark Side of the Moon. Perhaps you were thinking of Eclipse or Brain Damage, which both contain the lyric "Dark side of the moon." in the song. (The man brunt of the song is about the "killer in the hall".)
I can narrow it down to 4:
Heroin-The Velvet Underground
Schizoprenia-Sonic Youth
A Day in the Life-The Beatles
Like a Rolling Stone-Bob Dylan
Schizophrenia drew me the most problems-it's hard picking a favorite song from Sonic, but I generally regard that song as being perfect, in that there isn't anything I'd change about it. So it won out over so many other songs.
Mmmm Bop - Hanson j/k
Actually, I've never really thought about my favorite song. I guess I would have to say that my favorite song, as of now, is....ah hell, I don't know. Maybe How to Disappear Completely by Radiohead. Great song!
"Paranoid Android" by Radiohead and Dave Matthews Band "Crush" & "#41". right now i just can't seem to get some of the new Tool songs out of my head, and i grow more and more attached to them every day...
btw- there's a similar thread in the Polls area.
Stay- Coal (If ya dont know, it plays in Chasing Amy when Holden and Alyssa break up, but thats not all of it)
Streets of Philidelphia- Springsteen
Father and Son- Cat Stevens
I think favorite songs are determined more by the circumstances surrounding a listener's life at the time than by the quality of the song (although that counts, too), so the emotional importance of the memories attached to a song are often an crucial factor in what a person considers to be his/her favorite song. Mine, and for that reason: YOUR WILDEST DREAMS by the Moody Blues. Happened to be popular at a very fulfilling time in my life, on top of the fact that it has a great melody and performance.
Thirty Three currently holds my favorite video title also. If you have never seen it, do yourself a favor and fork 15 dollars over for TSP's video comp DVD. Its brilliant camera technique and set design makes it well worth the CHEAP price.