What can you ride in minecraft pc?

Other than boats and minecarts, nothing without mods. There are mods that allow you to ride existing mobs, as well as mods that add whole new mobs that can be ridden. A good example is mo creatures, which adds elephants, Komodo dragons, wyverns, ostriches, and more that can be ridden.

In vanilla Minecraft you can ride Pigs, Horses, Donkeys, Mules, Mine Carts, and Boats.

There are many, many, many more options once you start talking about mods.