Other forms: ball and chains
A ball and chain is a device that was once used to restrain prisoners. You can also call something that's a burden or makes it hard for you to do what you want a ball and chain. Just don't call your mate one!
The original ball and chain was a heavy metal ball attached to a prisoner's body with a thick chain (weighty enough that it kept them from running away, or at least from moving quickly). These restraints were common in seventeenth and eighteenth century Britain. Today, a ball and chain is more likely to be some obligation or responsibility: "My herd of dairy goats is my ball and chain — I have to milk them every day, so I never take vacations."