9. Sherlock vs. Moriarty Sherlock ('The Great Game')
Everybody's favourite British sleuth (and in my opinion the best incarnation of the character in any medium) comes face to face with arch-villain Moriaty in the first season finale. Having just solved a series of tantalising cases in a game of wits against his most fierce nemesis, Sherlock and Moriaty meet in person for the first time at the scene of Sherlock's first ever case. Watson gets thrown in wearing a live bomb jacket for extra tension, and there are also sniper dots trailed on our heroes. The scene de-escalates once Moriaty warns them off prying into his good work, and Sherlock removes the bomb jacket from Watson, sliding it away along the floor. Alas, Moriaty comes back, he's "so changeable" and can't allow them to go on. In the final standoff, Sherlock aims his gun at the bomb jacket between them. Moriarty smiles, and before Sherlock fires, the credits role and the season ends. You could argue that the cliffhanger ending in season two has more 'wow' to it, and that also ends on a cut-to-black, but I went for season one because I think the use of the technique is more appropriate here, it's all part of the same scene (the climax ends on a cut) where as the climax of season two (Sherlock jumping off the building) is then followed by closure scenes, before the cut-to-black is made after the reveal at the cemetery four minutes of screen time later. An honourable mention for season two though.