Van Halen 1 - Runnin' With the Devil
I like to imagine what people were thinking back in 1978 when this album first came out. You put it on and the first thing you hear is RWTD. Aside from the fact that it has one of the greatest guitar tones ever recorded, it's a pretty basic, easy song. A 10 year old with a basic knowledge of guitar playing could pull off the solo with little effort. So the listener is all "Hmph. Pretty straightforward stuff here, nothing to get excited about."
Then, it happens.
The moment that nobody who'd just listened to RWTD for the very first time probably ever expected.
Eruption.
A fucking freight train of notes and awesomeness barrels into you like a school of eels who have just seen something that eels like a lot. Complete barn-burning reckless abandon. At the time, such a moment of musical insanity was probably pretty rare to be captured on tape. I wasn't even 3 at the time, so maybe it was common. But not like this. It was different. Completely different.
After the last Echoplex-drenched note subsides, the entire remainder of the album kicks your ass all up and down the street. It's a roller coaster ride for the ears. It's like RWTD was a fake out, to lull people into some sense of la-di-da or something, so they'd be caught completely unaware when Eruption came on.
None of this is meant to diminish, in any way, the awesomeness of RWTD. Still an absolutely amazing song, despite its simplicity.