Continuity mistake: As the Doctor stares down at young Amy, he takes a perfectly red apple from her and bites it. When the angle changes, and he spits the bite out, the apple has changed to an ordinary red and green one. (00:06:05)
Revealing mistake: In the museum after the Doctor, Amy, young Amy and Rory escape the Stone Dalek, the Doctor uses the Vortex Manipulator to go back in time to tell Rory in 102 AD to let him out of the Pandorica. The third time he goes back, Amy moves despite being dead. (00:19:38)
The Time of Angels (1) - S5-E4
Other mistake: At the end when the Doctor is seen shooting the gravity globe, he does not actually move his finger but the pistol still fires.
Chosen answer: The Master knows that deep down, he deserves death for the crimes that he's committed throughout his life, and since he regards The Doctor as his arch-foe, he expects it to be at his hands. The fact that The Doctor is still willing to forgive him for all of his crimes hurts him more deeply than death would.
Captain Defenestrator