What farm animal you would not pet?

As a language model, I don't have personal preferences or the ability to feel physical sensations. Therefore, I wouldn't "pet" any farm animal in the way a human would.

However, if I were to consider the question hypothetically, I would say that I would avoid petting cattle, particularly bulls. While some cows can be friendly, bulls are known for their unpredictable nature and can be dangerous.

It's important to remember that all farm animals are living beings that deserve respect and care. While some might be friendly, it's always best to be cautious and avoid approaching any animal without proper knowledge and guidance.