I voted for Tactics Legolas, as I think there is a lot to be said for reasonably low threat specialized heroes. Due to his fairly low threat 9, his specialized nature with 3 attack and few wasted stats, his sphere and trait combination granting easy access to excellent weapons, and his ranged keyword, Legolas can slot into a lot of different decks and always pull his weight.
Thurindir is a hero I have been playing with more frequently lately and I have to say that he has become one of my favorites - his ability to start with any side quest is actually pretty amazing... even if Gather Information is the only side quest you include, it makes him a low threat 3 willpower hero and gets you that essential card early, really opening up deck building options. If you include additional side quests, his ability essentially allows you to tech against the scenario. Lots of threat increases? Find Double Back. Lots of minor enemies? Get the tactics quest that reduces non-unique enemies attack by 1. I like him quite a bit more than Gandalf, and am sad he is currently loosing a fairly lopsided vote.