I'm going to second The Lord Wierd Slough Feg recommendation. Down among the Deadmen and Traveler are both essential albums.
Pentagram(Mezarkabul) Is another great, start with Anatolia, then Unspoken.
Skiltron, Basically power metal with bagpipes. Beheading the Liars is the album I'd recommend starting with.
If you can deal with harsh vocals, Imperanon's only album Blade is fantastic.
Some honorable mention goes to a few others, Wolf (The black Flame) Missa Mercuria, Just about anything from Skyclad is worth checking out, Riot (Thundersteel) Anathema (A natural Disaster) Destiny's End (Breathe Deep the Dark and Transition are both AMAZING.) anything by which Devin Townsend has used his name on it's label.
I don't know what all you've already listened to, so some of this will probably be redundant, but tehre's also a slew of more obvious acts i'm not going to bother mentioning since everybody and their uncle has heard of 'em.