It might come as a surprise, but I'm really digging Trec. Trec ranks as the "worst" Cavalier in The Binding Blade (For good reason), but I love a defensive Cavalier. FE6 Hard Mode is hard (Shocker, I know), and hax is real. A tanky unit that isn't an awful-mobility Knight/General comes in handy when the game starts throwing dozens of Wyvern Knights at you. Trec isn't the strongest, most accurate, or fastest, but he has the best survivability.