Many many good songs that sound better at loud volume were mentioned, especially Who Are You and Baba O'Reilly. But, I can't believe that nobody mentioned the greatest rock song ever made...Won't Get Fooled Again!
I get goosebumps at the opening synth riff, and the hair stands up on the back of my neck when those guitar chords come thundering in. I sh*t you negative.
I highly recommend everyone pop the CD into their stereos, download the MP3 into their PC, login to iTunes, tune to Sirius 10, whatever it takes to hear the song again, and crank it up to 11. RIGHT F-ING NOW!!! I'm not kidding.