I definitely smell potential here. People who breed porn horses are completely underserved.Just pick one that NEEDS a website or whatever you need, has the money, and start hitting it.
Your question is pointless.
There's a million different markets. For example, add pornstars to your list. Or horse groomers. Or porn stars that do horse porn. Anything your brain can think of. Anything that exists. Writing out a list of all the "markets" is pointless.