What do you think are the most recognizable song intros ever? What songs do you hear the first two notes and say, "YES! Rock!"? In terms of recognition, I mean to everyone. I could tell you any Weezer song by the first two notes, but I don't think a random sampling would know more than one. Also, lyrical intros don't count. I have a ton, but I'll start the list with:

"Welcome to the Jungle"- GnR
"Smells Like Teen Spirit"- Nirvana
"Lust for Life"- Iggy Pop