Hachiko, Greyfriars Bobby, Fido, Shep, and every other dog on all three subsections of this list
By the way, to get the full tearjerking experience, for every dog on that list that has a full article, read it as well. -- RecklessPrudence
Etta was getting used to it, even though it broke her heart. Every day, for their morning walk, Boy would insist on trying to find his Master. The routine included visiting his former home in the JOAT sector, and visiting the small tree where his remains were laid to rest.
She let Boy lie under the sapling for ten minutes before she gently reminded him that he had work to do with her.
She wasn't his person. She was... someone who looked after him and worked with him. Boy was happy enough with her, she could tell. But he wanted his Master.
Etta let him do these things. Every day. Even on her days off, her days always contained a walk to the JOAT sector, and then a walk to the graveyard. She tried to teach him what death meant, that his Master wasn't coming back from his 'forever sleep'.
She would never know if he understood. He was an Augment, and not very bright about things. As easily distracted as a kitten in a discotheque. And sweeter than any mastery of culinary chemistry from Unsuitable Food Eat.
On the really rough days, she treated him to blue steak with peanut sauce. Not because he was having a bad time, but because her heart was breaking. And it happened every time Boy said, "No cry, Boss. Boy find Master. Boy keep look."