I'm not one to pay much attention to solos, or remember them, but here are a few that have stuck in my mind:
Dan Swanö - Uncreation
Dark Tranquillity - Edenspring
Dark Tranquillity - Zodijackyl Light
Amon Amarth - Where Silent Gods Stand Guard
In Flames - Everlost (II)
Eucharist - The Eucharist
Opeth - Black Rose Immortal