WHAT THE FOX SAY?
Assuming their domesticated enough to listen to my commands and ignore their pray drive, on like a magical level, Tiger. Hands down. I would go to the Renaissance Fair with them and commission a blacksmith to forge armor for them. I would ride it into battle whenever necessary.
Edit: I was also assuming no one else has a magically domestic animal. If everyone in this thread also has one, I'll choose Rhinoceros
the human one
Tigers are just big cats.
Red Panda. I want to steal one from the zoo every time I go.
Don't know quite how things would work out, but definitely domesticat the North American beaver because they're one of the coolest animals and you can't convince me otherwise.
Fruit bats. Just no ebola, please.
Kind of surprised that I'm not seeing honey badger or wolverine or tasmanian devil.
Opossums.
One that's big enough to cuddle us. They also should get along fine in the increasingly small environments we are being shoved into. Having a newly domesticated animal that is limited to the ultra rich with giant estates is pointless, right? Bonus points if we can make it an environmental win as well.
Just about everything 'big' fails at being in an apartment though. Big cats, even the smaller ones among them, need more room. Same with bears, moose (cooool, dudes, am I right? Imagine lounging with a moose), elk, whales, dolphins... bah.
My idea, then? Giant birds. Big enough to lay on you when on the couch, but could be let loose to fly around while you're at work. It would take an incredible amount of domestication to get them to go and come back, but if we're talking hypotheticals and theoreticals and blue fantasy, I think giant birds would be the way to go. Take your pick of them. The steller's sea eagle and especially the phillipine eagle speak to me, but I wouldn't turn my nose up at a swan, a goshawk, or a red kite. Feed them well at home, pretend that during the domestication process we made the nesting area easy to clean, and imagine being able to set it loose on stupid fascist leaders.
Parrots can be extremely intelligent, but are still dinosaurs.
Snow leopard
Red fox would be great assuming domesticated would render them not smelly xD
Miniature gm giraffe, about waist height. Cantering about with its tiny blue tongue. I love that little freak.
Yeah, bears for sure. Little teacup-size pet bears.
Otters
Zebra or giraffe. Not to ride, just to go on walks with.
Tiger!
I think a wombat would be cool to have around the place, assuming domestication allowed for some level of trainability.
One of my old uni lecturers was very keen on the idea of domesticating the spotted quoll. He reckoned they would make a great pet for those who would otherwise get a cat (a convincing argument actually).
Wasps; I'm going to be a supervillain now.
Edit: Scratch that. Termites have better crime potential, if that's the idea I'm going with.
Even if not, a large quadruped is the wrong answer when we already have dogs, horses and elephants. Something flying, digging, tiny or aquatic is where we should all be thinking.
I mean, obviously a lion.
Pallas's cat