25. "Guess Who's Coming to Dinner," Grey's Anatomy
Anyone who doubted that Grey's Anatomy could carry on without Derek Shepherd needs only to watch Season 12's fifth installment (and the show's 250th overall) to allay those fears. "Dinner" is Grey's at its finest -- with snappy writing, great performances (Ellen Pompeo and Caterina Scorsone in particular), tension that builds throughout the hour like a tightening noose, and yes, even a few hilarious moments thrown in for good measure (yay for drunk Arizona!). It also sets the stage for the new direction the show will take in its P.D. (Post-Derek) era, introducing us to Penny, Callie's new girlfriend who, coincidentally, is the same doctor who treated Derek after his car accident and whose mistakes likely cost him his life. Though Penny and Meredith are the only ones who realize the connection, when her secret comes out midway through the hour, it lands like a bomb. This is one dinner party we're happy to have watched from afar.