Guts is a companion dog that first appears in Fallout New Vegas Mods: Bounty Bonus Quests - Part 2. He travels with Al and the group and also appears in the subsequent mod review Fallout New Vegas Mods: New Aerotech - Park 1 and is a temporary companion.
Guts is found in Westside by Al and the group and his previous owner is already dead. Next to Guts is a trail of blood and a note written moments before the owner died. It reads that Guts was his only true friend, better than his ex-wife, "because at least a dog won't fuck the neighbor and steal everything you own", to which Al remarks that "you never know". The note also reads that if Guts is still alive when someone finds the note to take care of him. The owner then died before he could finish the next sentence.
He is alive at the end of both mod reviews, although it is unknown if he will appear again.