Strongman (and strong woman) competitors have been using "Axle" bars for years. Axle bars have thick grips- 2" vs the 1 1/8" shaft of a normal barbell. These axle bars make lifting harder as most people cannot close their hand fully around the bar. Working an axle bar into your routine will result in stronger grip, thicker forearms, and a stronger back.
Axle bars are most well-known for deadlift movements and for shoulder-to-overhead presses, but are also great to work in to your routine for bench press, farmer's holds, zercher squats, bicep curls, and more.
However, axle bars are not the greatest choice for a primary barbell since their collars do not rotate, making them a poor choice for Olympic weightlifting or similar lifts.