I've tried to choose just one, but it's too difficult to decide. Miklagard Overture, probably. But I like Cursed Be Iron, The Dnieper Rapids, Jarisleif and... Well, you get the picture.
1_ Miklagard Overture. Simply because is the best in every possible way.
2_ To Holmgard and Beyond. Perfect intro and a very epic song.
3_ Cursed be Iron. The riff and the song itself are both heavy as *paska(as the finnish would say)*. Plus the lyrics has some cursing on it(?)
I love To Holmgard and Beyond and Miklagard Overture, but I chose Portage to the Unknown for those four notes leading up to the ending "BRANDED AT BIIIIRTH WITH THE SIGN OF PERUN", 'cause that is probably my favorite single measure of all time