Stephen smashing a bottle and attacking Diamond Dog with it when he tries to intimidate Bloom.
When Penelope blows up her mansion.
Bloom pulling a gun during the final confrontation, showing his Character Development from the paralyzed and passive role the Diamond Dog knew him to take.
After we spend the last third of the movie wondering whether Stephen would really con Bloom Stephen takes a bullet for his brother and pretends it was fake, just to give Bloom a happy life with Penelope.
Stephen finally pulls off the perfect con, in which "everyone involved gets just the thing they wanted." Bloom gets his unwritten life, Penelope finds an end to her loneliness, and even Diamond Dog gets his revenge. And pulling off the perfect con was just what Stephen always wanted, too.