Sledge hammer workouts are very trendy today. They help you grip, shoulders, triceps, upper back, lower back, hip flexors , and core while being great for cardio. The main benefit for boxers and fighters tend to be the mental aspect of hitting through an object while keeping your punching muscles tight. You get to practice over and over again getting better feedback than when you hit a punching bag. If you want power always try to drive through the tire to the ground, not just use the recoil to get more reps.
Priorities
Better myself mentally>Better myself physically>Picking up girls