Disclaimer: Pets are a long term commitment and can require years of care. Please take your own skill level, economic resources, home situation, and schedule into account before adopting a new friend.
I wouldn't feel right starting this list with anything other than a Cat. Black, if you want maximum Goth points. Above is a picture of my cat Zoot! (Yes, with exclamation point included) who I love dearly. Healthy indoor cats can expect to live up to sixteen years and there are a variety of fun goth-appropriate cat toys available especially around Halloween time. And why not pick up a black coffin-shaped cat bed from Etsy while you're at it?
Pygmy Goats are an extremely cute option if you're ready for a high-energy, very friendly pet that looks a little bit like Satan when it grows up. They are very sociable but might not necessarily need a herd if there are plenty of people around for them to love in. Expect pygmy goats to live up to a decade or more. Unlike many of the other animals on this list, Pygmy Goats are prey animals so be careful with any predator animals you might also be keeping. Like a leopard. Or something.
Gypsy Vanner horses are next on my list because, while they're not exactly practical for everybody, nothing screams gawthick romance novel like a big black horse (preferably ridden by a handsome rake whose shirt is perpetually unbuttoned.) Horses require huge amounts of exercise, expensive food, and stable lodgings with other horses as they are social animals. Horses can live for many years and are definitely not for the faint of heart. But hey, you can ride them sidesaddle in your Victorian finery.
Rats, more specifically Fancy Rats, can make for great pets if you know how to treat them right. Some of them can be extremely cuddly and are known for riding around on their caretakers shoulders. Rats are social animals and it is best to have multiple at a time, but it can be difficult to find a quality breeder. They live for a few years, certainly less than other animals, but with proper care can make for wonderful companions.
African Pied Crows are actually legal to own as pets in the United States, as are other species of crow and raven that are not indigenous to the USA. While these birds are not the famed all-black ravens and crows you may be used to, they're still extremely beautiful. However, they live for many years, require a specialized carnivorous diet, and lots of space to spread their wings.
Lop-eared Rabbits are almost every five year olds dream animal and they're still so precious to this day. While they are not naturally the most cuddly of animals (and aren't too fond of small children), they can form bonds with their caretakers. They are herbivores and if you're awesome you will name your rabbit Bunnicula because come on how could you not.
If you want something a little less leg-y, how about a Mexican Black King Snake? These non-venemous snakes live over a decade, prefer not to live with other animals, and primarily eat rodents. They are mostly nocturnal, but don't particularly mind being held (unless they are shedding) and make wonderful companions.
Again, I'm not trying to suggest that my readers should go out and buy a pet just because it is Goth-y without looking into the pet's care and making an educated decision about whether the pet is right for them. I am suggesting that it's worth expanding your horizons, and some pets are spookier than you might expect!
What pets do you all have, and do you think they speak to the Gothier side of you?