Squats target your quadriceps, but they also activate your core and just about every other muscle in your lower body, including your glutes, hamstrings, and calves.
How to do it: Stand on your left leg with your hands on your hips. Extend your right leg in front of you, bend your left knee and slowly lower your body until your left knee is at a 45-degree angle. Pause, then push yourself up. Perform 10 reps on your left leg and then switch to the other side.