Rufus

 is a minor character featured in Red Dead Redemption and the Undead Nightmare Pack. He is the Marston family dog; a yellow Labrador Retriever, he accompanies John and Jack on several hunting missions near the very end of the story.

Background
Not much is known about Rufus, other than he is a good tracking dog. In the final mission, he presumably goes missing or is killed. It is likely he escaped as the soldiers focused more on John Marston and his family rather than anything else, although it is confirmed the soldiers do shoot at Rufus when he is out in the open. He can usually be seen roaming around Beecher's Hope after the main storyline is complete, never having left the home of his owner even after his death.

Red Dead Redemption
Rufus appears in the mission "John Marston and Son" where he assists in tracking down elk. He then assists Jack and John in the mission "Wolves, Dogs and Sons" where he assists in tracking down packs of wolves. Rufus then assists John in finding Jack during the mission "Spare the Love, Spoil the Child". Rufus is last seen running behind the house during the mission "The Last Enemy that Shall Be Destroyed".

Undead Nightmare
During the mission "Love in the Time of Plague", Rufus is seen being chased behind the house by the Undead Jack Marston. His fate after this mission is unknown.

Trivia

 * Rufus, Charlie, and Lucy are the only named domestic animals in the game.
 * Some players have speculated that Rufus was killed, since he was going around the back as the soldiers came, and, when Jack goes around the house, he is no where to be found. But his corpse is not seen hinting he might have escaped. However, it's more likely that Rufus died because of natural causes during time between 1911-1914. He has however, been seen sitting down behind the Beecher's Hope house after the main storyline is completed.
 * Rufus appears to be a yellow Labrador Retriever, not to be confused with the Golden Retriever. (Golden Retrievers have a longer coat.)
 * During the mission "The Last Enemy That Shall Be Destroyed", if you follow Rufus, he will keep walking until he gets into a small room, where he will continually move as if dodging something. If the player moves their camera away, and then moves it back, they will discover that Rufus has disappeared.
 * Sometimes if the player kills a dog while playing as Jack Marston he will say "I guess I just miss Rufus."
 * Sometimes Rufus can be found inside the House (Beecher's Hope) and is found in Jack's room and lies down until he wakes up.
 * At the beginning of Undead Nightmare, while John is tying up Abigail, Jack can be seen in the background chasing Rufus.
 * If the player kills Rufus, like when killing members of John's family, the game will fail.
 * On rare occasions two Rufus dogs will spawn, but the player cannot kill both of them.
 * Rufus may be killed by a cougar, should one enter Beecher's Hope. This does not affect missions, however, and he will simply respawn.
 * After the mission, "The Last Enemy That Shall Be Destroyed", Rufus can be seen sitting in Jack's room on the rug. It is possible to nudge Rufus out of the house, however after that he will just run away and if you move your camera off of him just once, he will disappear.