The Last Of The Starks - S8-E4
Revealing mistake: At the beginning when all the dead are burned, we see a close up shot of a dead guy still breathing.
Battle of the Bastards - S6-E9
Revealing mistake: When Jon Snow jumps on the horse his steel sword wobbles back and forth revealing it's made of rubber.
The Watchers on the Wall - S4-E9
Revealing mistake: Castle Black defenders drop heavy stones on the free folk and one of them gets hit on the head but forgets to act injured (or dead). (00:23:20)
And Now His Watch Is Ended - S3-E4
Revealing mistake: When Karl kills Craster, you can see the blood packet in Craster's mouth right before he spits up blood.
Suggested correction: It's not a blood pack. It's Karl's blade.
Revealing mistake: At the beginning of the episode, Robb and Blackfish Tully are pushing Hoster Tully's funeral boat down the river. When they climb back onto the dock, there is already a trail of water going from the steps and ending where Robb ends up standing. None of the other characters standing on this portion of the dock have wet clothes, meaning none of them went into the river, indicating that the trail of water was from previous takes.
Revealing mistake: Just after Jon is told he is confined to quarters, there is a shot of outside with snow falling. However the snow is actually rising. Indicating the shot has been reversed. (00:22:55)
Revealing mistake: When we see Joffrey get attacked by the dire-wolf, You can see his arm suddenly has padding underneath his jacket. (00:47:20)