stability balls, physio balls, swiss balls, balance balls, exercise balls--call 'em what you will-- I
my stability ball.
It's a great piece of equipment for the home workerouter. You can do so much with it! You can use it for abs, for stretching, for relaxing, as a substitute for a bench to do dumbell work on--you can even use it for cardio!
And when you're not using it--- it becomes an extra seat.
Plus, it's fun to play with balls! I also have a medicine ball that I use, but it's not as versatile.