Dear 100 Hour Board,
Oh dang, now I want all of those powers!! Especially Super Social Strength. And to be able to turn into an Alpaca!
You get your Hogwarts letter; which pet do you take?
-Cat (tabby, siamese, ginger, black, or white)
-Owl (tawny, screech, brown, barn, or snowy (you were waiting for that one, weren't you?))
-Toad (common, natterjack, dragon, harlequin, or three toed tree toad - say that fast!)
-Rat (common, black, or animagus) jk, rats aren't actually allowed at Hogwarts!
I know owls are probably the most basic answer but let's be real: they're a free mail service subscription. I will choose functionality over novelty every time. I would have a barn owl because they're the prettiest. I would name my barn owl something noble like Atticus or Calloway.
I would probably get a cat, because I like cats. Yes, owls are more practical, but I can't help but feel like they require more actual care than the Harry Potter books let on. Plus, I relate more to cats' personality than most other pets.
A black cat would be my first choice, though ginger and tabby would both be fine. I wouldn't want it to have very long hair, either.
Not cats, because I'm not really a cat person. I love the idea of a cuddly cat that would sit in my lap as I studied, but I could just as easily end up with a mean cat that hissed any time anyone got near it. So much about your cat just depends on luck of the draw, and I don't live that kind of life.
Not toads, because is anybody on this earth a toad person? Gross.
Not rats, because although I suppose some people like them, their scaly little feet and long bald tail don't appeal to me in the slightest.
So I guess I'm left with the most functional of all the options, owls.
I'm almost tempted to choose screech owl so that my pet could look at people like this
but I think in reality I would choose a barn owl, because, like Babalugats, I think they're the prettiest of all the owl options listed.
At first I thought I'd get a snowy owl (owls are just so useful!), but on further reflection I realized that, if I'm really in the wizarding world and will be fighting against evil people with dark magic, I probably don't want to send my ultra-secret messages by the most obvious of owls. A quick google search revealed that tawny owls are the most common owl, and would blend in perfectly. That way, my owl wouldn't be easily seen and picked off at night as it fought to help me (Yes, I'm sorry, I went there).
-guppy of doom
I've kind of made it into a personal challenge to somehow squirrel my way out of using any of the options you mean while still technically using the options stated in your question for my answers (in other words, I've been attempting to live out the letter of your questions whilst avoiding the spirit). However, some 100 hours after picking this question up, I must admit defeat and concede the high level of specificity detailed in your question that does not allow for much deviation.
But wait... I just had a stroke of inspiration for how I can yet again evade an answer in alignment with the spirit of your question! For Hogwarts is a school of witchcraft and wizardry. And that of course leaves room for magic to work its spell.
So, I'm going to choose an owl. But this owl will have been on the end of an engorgement spell gone wrong (or some other such similar enlarging kind of magic), and thus be large enough to carry a human on its back whilst in flight. Specifically, it will be large enough to carry me on its back.
Cat. Tuxedo cat. Specifically my tuxedo cat, the Mitty Kitty.