Here is a link to a prestige class that interests me.
The basic premise of the class is that you take a neat companions, and you and it fight together as one creature, and share some stat bonuses from time to time. For the purposes of this, please note that races are NOT basic PF 1 races. They are all on the host sites wiki. There are 3 large races, Liontaurs, Centaurs, and Minotaurs. They all have natural attacks, so they'd gain a bite at best.
I'm thinking a Medium character and something like a badger, since it gets some good abilities, and I'd get rage out of it, but I'm sure someone else can help me out more than that.
Maybe a Centaur with a Horse companion? That though, creates an abomination in my minds eye when they merge using Synthesis!
This should probably be posted in a 3rd party forum. There are a number of things here that a way out of normal for pathfinder.
You might be able to use some of the ideas from this thread though.
Same as A_K. I'd help but I don't own the product and I'm not going to dubious web pages.