Great thread!

My personal fave from this list is Malmsteen because I like his sense of voice leading more than the other guitar shredders. The way he approaches soloing over the very tonal chord progressions he uses is a thing of beauty to me.

Ren mentioned Shawn Lane. And to my knowledge he is by far the most impressive in terms of sheer technical facility. But I don't like the majority of what he plays. Just not my aesthetic style.

Also, Allan Holdsworth is worth mentioning in this context, even though he is more jazz fusion than rock, per se.

Finally, don't forget the original shredders: Niccolo Paganini (violin) & Franz Liszt (piano). Search for some people playing pieces by those guys. Yikes! And I must mention another personal fave of mine that was a shredder but on piano and in the genre of jazz: Art Tatum. That guy was amazing. :)