Continuity mistake: Ash has his shotgun stolen from him by the mini-Ashes who use to shoot at him. Ash then runs outside (all the while splitting into his good and bad halves) leaving his gun inside the windmill. Moments later Ash now has his shotgun again so he can blast Evil Ash in the face.
Continuity mistake: At the beginning when the wise man says to King Arthur something along the lines of, 'I believe he is the one written off in the Necronomicon. He who has been prophesied to fall from the sky and deliver us from the terror of the deadites,' He is sitting on the horse to the right of King Arthur. When King Arthur says, 'What? Who? Likely he is one of Henry's men,' the wise man is now on the other side of Arthur.
Continuity mistake: When Ash is driving his modified car crushing skeletons and such, a skeleton jumps on the side of his car. Ash shoots him with his shotgun and A) the shot from the shotgun is it front of the skeleton (not hitting him), and B) when he says "Bye Bye", his mouth does not move.
Continuity mistake: Ash, Henry, and the other prisoners all have clean, non-sweaty faces and neatly combed hair after trekking across the hot, dusty lands in the "chain gang" line. This is particularly noticeable on Henry just after Ash demands that the prisoners be set free; even his little hair decoration is still in place.
Continuity mistake: In the shot where Arthur's men have just started the spiked walls moving in the pit, Ash looks at the walls intensely. In this shot, if you have the full screen version on, you can see that his chainsaw is attached to his hand. They use that same shot later on right before he charges over to climb the wall.