Every guy who goes to the gym on a regular basis is familiar with dumbbells, kettlebells, and barbells. They're not only essential pieces of equipment to circuit-based and weight training routines, they're also straightforward and it's relatively easy to learn how to execute proper form.

But there's a lot more to fitness equipment than just the basics. Incorporate lesser-known, under-appreciated tools—like the parallettes or sandbags— into your sweat sessions you'll start to work muscles you didn't even know you had.

Here are 15 pieces of under-rated gym equipment you should start incorporating into your fitness routine.