As the title asks. Imagine by some weird reality breaking whatever you could have any Pokémon you wanted as a pet. One, though. Which Pokémon would you consider and why?
I'd go for Articuno, Suicune, Entei or Raikou (most likely Suicune).
Suicune most likely because, at my current height/weight, it would be easy to ride on it's back, therefore I could get places extremely fast as well as not having to use public transport (due to the fact I get on buses for free, I tend to get stuck sitting next to strange smelling old ladies).
(Entei and Raikou for the same reason).
Oh, and Suicune could freeze a certain Twatty McTwat I know...
Articuno, because I might possibly be able to ride it even though it's only a little bigger than I am, and even though it's an ice-type it's feathers look snuggly and warm to hug.
Note how none of the ones I want as pets are my favorite Pokémon :B