What are the best couch/local co-op PC games?

Even though you choose a class when creating your character, it only affects your starting equipment. You can create a character build with any skills you like without class or archetype constraints. This includes a fire mage that wears heavy armor while wielding a shield and a hammer, an archer that can use teleportation magic to always keep the distance, and countless more. You even get to build your companion characters from the ground up, allowing for hundreds of party combinations.

As an added bonus, once you complete Act 1 of the game, you can respec your build whenever you want, free of charge. Because of this, you don't have to worry about messing up your build, allowing you to freely try out any skill combination/setup.