Is there a song that you can't help but sing when you hear it?
I'm on a bit of a Maiden trip right now (or should that be voyage?) and I've just noticed that Hallowed Be Thy Name does this thing where when I hear it my mouth sings the words!
Yup! I'm guilty of doing that with "Run to the Hills" and "Rime of the Ancient Mariner" - and want to head bang along too.
Also guilty of butchering the guitar solos with vocal renditions quite shamelessly.
As for non-Iron Maiden songs I have to sing along to: RATM's "Killing In the Name" or "Bombtrack" - it's a pavlovian reaction to the baseline, I swear.