Kettlebells
I workout with them. They're just another toy to help prevent boredom for me.
They're just another form of weight and definately not for everyone. They tend to really bang up the forearms if you're not careful. Trainers like them because they're new and different to most people, but they started off back in the 1800s as scale counter weights.
I have a 20 k and a 40 k that I do swings and juggle with just to warm up or play around with.
Earl