I could probably choose hundreds. I cannot choose only one. So here are a few.
Subdivisions-Rush. I've told Geddy so many times he's sick of hearing about it. I grew up during my final teen years on a dead end street in the suburbs on the edge of my hometown. At nighttime there was one streetlight a few houses away. Towards the NW was only darkness and the night sky that seemed to go on forever. It truly gave the illusion that I lived on the edge of nowhere. To the SE was the constant glow of the big city. I used to sit on quiet, cold winter nights and dream about all the amazing adventures that I was going to have once I got out of that little town. When that song first came out, it touched my very soul. To this day, each time I hear it, I'm transformed back to the sights, sounds, smells, and emotions of that time. I'm a firm believer that stuff happens for a reason. That God, or the Great Electron in the sky, or whatever has a plan he or it only shares occasionally with us. I believe that there was a reason that song touched me the way it did, and I later not only met, but befriended Ged and Alex. Ged calls it "Tsufal", which is supposed to mean coincidental or something.
Wasted Time- Eagles. To me clearly Don Henley at his very best. And I've lived that same heartache more than once.
Let It Be- Beatles. Blows me away every time I hear it. Instantly takes control over whatever emotion I'm feeling at the time.