5. The Walker Who Ate Lori
When Lori dies during childbirth in the season three episode "Killer Within", she is shot in the head by Carl (so she doesn't reanimate as a Walker) and left in the boiler room of the prison that the group are calling home. In the following episode "Say the Word", suffering from severe grief at the loss of his wife, Rick goes on a killing spree through the prison, slaughtering every Walker in his wake, until he reaches the room that he identifies as the room Lori gave birth and died in (thanks to a knife and various birth fluids on the floor). But Lori's body isn't there. He follows a trail of blood until he sees a hugely bloated Walker who appears to have eaten her corpse and is so full that it can barely move. He shoots the Walker in the mouth, before repeatedly stabbing its full stomach while screaming in pain through grief.