John Lennon and George Harrison - John's sometimes-sloppy rhythm with George's beautiful melodies and accents make for a great pairing.
Robert Fripp and Adrian Belew - I struggle to think of a more talented pair. And when they do that cascading arpeggio thing, it's just awesome.
Angus and Malcolm Young - Neither are technical wizards, but together they form what is IMO one of, if not the absolute greatest rock guitar sounds.
Stone Gossard and Mike McCready - Maybe it's because I've loved Pearl Jam so long, but these guys play off each other really well. Their complementary parts just gell so well.
Now you go!