The Epic Riff in Money for Nothing. It's worth noting that in the album version of the song (which is 8 minutes long, thus the shortened version for the linked video), the song spends a full minute and a half building up to that riff.
In fact, when "Weird Al" Yankovic wanted to parody the song, Knopfler offered/demanded to reprise the riff himself.
"Tunnel of Love."
And, of course, the solo at the end of "Sultans of Swing."