An exercise ball is multipurpose

There are lots of exercises, especially for your core, that can be done with this ball.  

Works great replacing your desk chair as your turn the act of sitting into an active movement.

Over on Amazon here: https://bit.ly/GuudExerciseBall and be sure to look at the size chart to make sure you pick the right one.

It's 10-15 dollars and a great little addition to a budding home gym.