Pretty self explanatory. There are many people who love one particular rock sog...whether you use it to motivate yourself all the time, consider it your themese song, or it's just the one song you can listen to 40 times a day andn ever get tired of.
For me, I know it sounds dumb but- Master Exploder by Tenacious D. Short, simple, doesn't make a lot of sense, but I canNOT get enough of it.
I had to think about this a bit, cause my music is far heavier than rock but if I had to settle on one, I'd probably choose Detroit Rock City by Kiss. Always liked this song.