A velociraptor said:
The first time I heard the opening riff to "Layla" live.
Goddamn I love me some Clapton.
On topic, I highly agree with the Ennio Morricone that has been mentioned (it IS Ennio Morricone, after all). While I do not feel like "Unnatural Selection" is the best Muse song ever (and, believe you me, I am quite the Muse fangirl), I would vote for the slap-bass in "Undisclosed Desires" for most recent eargasm as far as they go, but I'm biased as a bassist.
For me... Well, I personally have a rather large playlist of "punch-out-Cthulu" songs, but one that consistently makes me want to take on the Devil himself is a song called
"Sometimes The Line Walks You" by a little band named Murder by Death. It's about breaking out of prison. Imagine yelling "JAILBREAK!" at a concert in a room full of others doing the same. I assure you, it is awesome. Apologies for the less-than-fantastic sound. I suggest Googling their Bandcamp page and listening to it that way (for free, no less!)