I'm a huge fan of twin bands with two guitarists, especially those who play twin lead. By this i mean they don't have one doing rhythm and one lead, and also they have a seperate singer, not one who plays. Just wondered who your favourites are. You can include rhythm lead partnerships too if you want. Mine are...

Dave Murray/Adrian Smith - Iron Maiden
Mickey Moody/Bernie Marsden - Whitesnake, Moody Marsden
Glenn Tipton/K.K. Downing - Judas Priest

And rhythm/ Lead :-

James Hetfield/Kirk Hammet - Metallica
Izzy Stradlin/Slash - G 'n' R

I'll probably come up with some more later...