I think rabbit would be cool. They're fast, so maybe a fire/electric type? Then, in that gen, each starter's secondary type could be good against its primary type's weakness. A water/bug? A grass/rock?
So we still have yet to see an Ox, Goat, Snake, Rabbit, Horse and Tiger for Fire starters. Although Snake was used for a Grass type Starter and there'a already Ponyta and Rapidash. I don't know if Arcanine and Growlithe counts as dog, or tiger, or both. So what's left is an ox, goat or rabbit.
I really dislike this being spread around just because it's so inaccurate. I don't just mean "Oh, well Fennekin is a fox not a dog." I mean that it's so inaccurate that there's no way Gamefreak even intended this to be true.
Cyndaquil/Typhlosion is a badger
Torchic/Blaziken is a chicken, hence chick.
and of course, Fennekin is a fox.
If Gamefreak intended this to be true, wouldn't they have simply just done the correct animals, Rat/Dog etc?
It just seems like this was pulled out of someone's ass because they noticed a monkey and a pig were in the chinese zodiac or something