He gets a Determinator moment with Porlock, proves himself a decent-enough tracker and a capable actor, delivers a Badass Boast to a prisoner while playing the Deadly Doctor trope straight, and rides halfway through London on a Cool Horse (Moran's uncooperative stallion, no less!).
In fact, Holmes can hardly believe it when Watson tells him just a portion of it.
And when Watson seesDeath, he refuses to let him take Holmes.
The face-off between Moriarty and Mycroft at the end. There's worlds of subtext in their brevity.
Holmes in his Let's Get Dangerous mode in the chase scene. Doesn't get much more awesome than a convalescent Sherlock Holmes shooting at Colonel Moran in a cab chase!
"Day 18: Long Time Falling" depicts the life of Professor Moriarty and the fight at the Reichenbach Falls with metaphors supplied by two different poems. At the end, Moriarty seems to regard Holmes's (simply called "the boy") victory as the detective's Crowning Moment Of Awesome.