Rush - The Pass: very simple, but oh so elegant. Incidentally one of the most beautiful songs I've ever had the pleasure of hearing.
"Comfortably Numb" solo. Not my favorite music to listen to but that solo with that chord progression... oh man... hits me right in the soul every time.
Steve Hackett (Genesis) playing the solo in "Firth of Fifth" is one of my all time favourite solos. Simple, but beautifully simple and just over the top melodic.