Ok so here are a few musts that haven't been mentioned:
Peter Tosch
Mad Professor (dub)
israel Vibrations
Ijahman
Jah Shaka
Groundation
Manu Chao
Steel Pulse
Augustus Pablo
Ok thats what is in my head right now, but there are hundreds of great reggae artists, compilations and albums out there. There are also hundreds of bad albums, so don't be surprised... (I personally do not like modern dancehall, I find it deprived of that smooth classical reggae vibe.)
^^^ to the post above me, I tottaly agree with you. the guitarist is unlike anyone, not in the fact that he is much better than everybody, but thathe has a unique style of playing.