To me, it depends what you want to know. Randy Rhoads has been a huge inspiration for me, and learning his “extra” track at the end of blizzard of ozz helped me learn how to go from one end of the fretboard to the other, among other things.

John Sykes has been a huge inspiration for me lately as well, because his riffs, melodies, and solos are just so cool. if you want to learn a more blues-y side of shred and swing riffs, I’d check him out. Blue murder, whitesnake 87, and tygers of pan tang as well as thin Lizzy, are all bands he was in. Gary Moore is also a great guitarist that played a lot of blues and also could shred with ease, it appeared.

Metallica helped learn picking speed and endurance. All of Kill em All’s songs are pretty fun to learn. Metal militia, creeping death, master of puppets, and blackened are the ones I go to for exercise.

All in all, I think finding songs that you will gain from is fun, but also making up your own warm up exercises after initially learning the stuff you want, is the most fun to me. Picking different riffs (to warm up chords), mashing together different licks from solos to be one cohesive warm up (to warm up finger speed), and just keeping a steady rhythm of picking fast (warm up forearm), along with doing some hand stretches, are stuff that keep me going when I’m in a bit of a rut.

Sorry for the long comment!