I do not own Fallout. If I did, this is how I'd do it.

Fallout: Orleans

Non-Human(oid) Companions

BDJ: The Baby Deathjaw

Deathjaws, unlike Deathclaws, can be tamed without the use of fancy controller collars. It's a hard, dangerous, costly business, but a valuable asset to those who can take the opportunity and have the time to let them mature… and a good profit for the Hunters and Trappers who do it.

For either a good deal of caps (say 5,000 at the barter discount from 8,000 standard) or an exceptionally hazardous quest in the Bayou (going in radioactive, Deathjaw-infested waters to find a lost Hunter), the Navigator can get a Young Deathjaw imprinted on them as a loyal companion. The 'dog' of the game, the Baby Deathjaw (namable by player, but everyone calls it something else) waddles after the player, rushes to bite things, and has exceptionally tough hide. It wavers between 'cute mutant gator-thing' and 'playful'.

The Deathjaw quest is that as it grows and matures (reaches level X), the Deathjaw starts getting violently aggressive. A chance for berserk in combat at the start, but also even attacking non-hostile characters. Once this happens the Navigator can go to the Tamers for assistance, and learns it's basically Deathjaw puberty/jealousy and that the thing is naturally territorially-possessive of you, especially if you have another companion. The player has a few options, some that require caps favors and some that don't.

If the player doesn't have the caps or doesn't want to do another option, the player can leave things be for now. A later choice is allowed, but for now the Deathjaw has the 'Possessive' trait that gives it a bonus to stats, but a risk for berserk/attacking non-Companion NPCs to 'prove' itself to you. This risk goes up by level, and by high levels is a near-guarantee for a fight in any town.

The player can put down the Deathjaw. Doing this kills the Deathjaw, obviously, but the player gets a unique perk (something like 'Putting Her Down') that provides bonus damage against all Deathjaws in the future. The Traders also offer to turn the loot from the corpse into a special set of Deathjaw leathers for you, which have superior stats to regular deathjaw leather clothes.

For a few thousand caps, the Navigator can 'bond' to the Deathjaw, appeasing it's jealousy and encouraging its protectiveness without it attacking others. Baby Deathjaw gets some significant stat bonuses, particularly to its speed and attack when it's the only companion, but it can NOT be fired or dismissed. (Excect for DLC, at which point Baby Deathjaw is waiting for the player upon return and automatically rejoined.) This option is good if you never intend to have the other non-Human companion, or just want one companion in general.

For a few hundred caps, the Navigator can neuter Baby Deathjaw. Baby Deathjaw loses the stat bonuses from its 'possessive' state, but gains a bonus to damage tolerance and will no longer attack others. Baby Deathjaw can also be fired.

If the player finishes the game without doing the companion mission, Baby Deathjaw eventually attacks someone in a town and gets killed by an armed mob. If player finishes the companion mission and Baby Death Jaw was neutered, Baby Deathjaw remained a calm and ever-loyal companion who disappeared into the Bayou after the Navigator died. If 'bound', Baby Deathjaw either fought to the death to avenge the Navigator's death (if Navigator dies in an ending), or remained an ever-present bodyguard who birthed litters of little Deathjaws that imprinted to the Navigator as well.

Author Note:

Baby Deathjaw (I never use the acronym personally) is the replacement for having a Dog. I realize having a Dog is something of a Fallout tradition- there's been a companion, if not much of a story arc, in every previous Fallout game- but I wanted to do something different. Part of it was fulfilling that silly little wish of 'why can't I have a badass Wasteland creature as a companion?', part of it was just for diversity, and part of it was because it made less sense in the context of a region in which the phrase 'eating dog food' refers to eating dogs as food, a degrading act of a desperate survivalist. Wild dogs are considered unclean, eaters of trash and known to cannibalize other dogs and the pack of weak cowards ganging up on individuals and innocents provide them a negative moral character in the Orleans context. Orleaners would listen to the tales of the most Good Karma Lone Wanderer going around with Dogmeat and think 'I knew there was a character flaw in there somewhere!'

Personally I think dogs are an under-recognized food source in the Fallout universe. I came to the conclusion during an analysis session of Fallout 3, where there were no major domesticated animal industries for food- no brahmin barons or bighorn herds explicitly for food. You had hunters, but the packs of wild dogs seemed like both a dangerous nuissance and yet a viable food source. FO3 never did anything with it, so it came into Orleans, and with a cultural aversion to dogs it didn't make as much sense for the player to get one by default.

Then came the companion decision between having the tamed deathjaw (a concept of the setting since the beginning), or a Bayou Bobcat (a later addition as the culture of Orleans and the Bayou was fleshed out). The tamed baby deathjaw (baby for balance) won out- partly out of inertia as the first contender for the role, part of the supporting lore that always had deathjaw tamers as Fallout-verse alligator handlers, and ultimately because I had a story concept in mind for the deathjaw but none for a cat companion.

As a final note, tomorrow will be the last companion. Any companion-related questions, and questions in general, will get a look there.

Secret of the Bayou:

First, the most obvious. The name Deathjaw was inspired by the conversation in FNV's Honest Hearts DLC in which a cocky wannabe shows his incompetence by confusing Deathclaws for Deathjaws. Even though the idea of a mutant aligator would almost certainly have existed regardless, the name stuck forever after that.

In setting, Deathjaws are a strategic resource. Fully grown, they are effectively loyal Deathclaw companions who, protective and territorial tendencies aside, remain almost unstoppable juggernauts of jaw-crushing destruction. Deathjaw handlers have always had a quiet but significant role in helping keep Bayou raider tribes like the Brown Waters away from the city. The First Consul created the first organized Deathjaw nursery to breed and tame Deathjaws in larger and more organized numbers, one of his few standing military policies of note.

When the Enclave came, one of the earliest things they did was destroy the nursery. The adult tamed deathjaw population was massacred, often from air by Vertibirds hovering over and unleashing gattling fire, and the Enclave Army went in to shoot the babies and stomp on whatever eggs they could. It was just one of many Orleans disasters of the opening years of the war, and Napoleon had the survivors and any Deathjaws that could be salvaged relocated deeper in the Bayou and hidden from the Enclave. Only now are the first post-invasion Deathclaws coming of age and starting to be deployed.

For now, the only tamed Deathjaws in the Orleans area are those raised independently by independent trappers and tamers. Though the Enclave has expressed interest in purchasing tamed Deathjaws, Orleans loyalty (and Orleans retaliation) has kept virtually all tamed Deathjaws going towards Orleans or exceptionally important independent buyers.

(And, now that I think about it, the Nursery never got into the Bayou locations list. For shame.)