This question always trips me up. Because honestly, my favorite song depends on my mood (based on weather, circumstances, wishes, wants, etc.) and if I am in a reminiscent state of mind or current one.
So my favorite song at this very moment is:
The Verve Pipe - The Freshman
This song has always been one of my favorites for some reason. It reminds me of the summer of '97...which was a really great summer for me. I was 14 at the time. I was reminiscing about that summer last night/today, which reminded me of this song. This song has nothing to do with my actual life, but I've always really liked it. Click the link above to check out the music video!