The final boss has Shield Knight fight alongside Shovel Knight once more.
The dialogue before the fight is great
Shield Knight: When the amulet shattered, the magic within it was released! It's already gathering. It will escape and wreak havoc on everything... Shovel Knight: Unless we stop it. Shield Knight: Unless we stop it! We can destroy it for good, here and now! Shovel Knight: But we're both weak from battle! Shield Knight: I've never been more ready. Come on, Shovel Knight, let's fight together, like old times. Now... stay close to me!
The duels with Black Knight are all awesome, but Yacht Club Games saved the best one for last. Black Knight, now revealed to be good, is forced by The Enchantress to fight via mind control. Eventually, Black Knight begins to sprout wings and rain meteors down on Shovel Knight. It's an exhilarating, amazingly epic conclusion to the rival fights.
Every boss fight is pretty awesome, but special mention goes to Tinker Knight's fight. It starts off very simple and embarrassingly easy. Then, after you completely deplete his health, the floor collapses and tiny little Tinker Knight leaps into a Humongous Mecha!
Shield Knight surviving her You Shall Not Pass moment in the end. Also, she didn't need Shovel Knight to catch her. It's appreciated, but she can take a fall. She's not the Damsel in Distress, they're partners.
The game had been subject to some severe schedule slip before finally reaching the target release on the end of June 2014. Why? Because they finished the Alpha build around January. And by Alpha build they mean THE GAME IS PLAYABLE FROM START TO FINISH! The devotion they have to making it perfect is astounding.