All-time? The Nirvana classic, "Heart Shaped Box." I love it so much, it's the first tune on my MySpace playlist. "Free Bird (Outtake Version)" by Lynyrd Skynyrd is a close second. Then there's the Goo Goo Dolls' "Iris," Van Morrison's "Brown-Eyed Girl," Tool's "Rosetta Stoned," Rage Against the Machine's "Killing in the Name," Moby's "Southside," etc.