Establishing good grips in grappling sports and MMA is extremely important as by dominating the grip battle and establish dominant grips, one can truly control and dominate the battle.
Many grapplers work their grips by climbing rope and doing pull ups with my gi. Rock climbing is also very benificial.
Many top BJJ competitors have used rope climbing as a staple of their daily training. Fernando Margarida was said to have spent at least an hour per day on his rope training.
Pull ups are also one of the best ways to build upper body strength.
In a sport like MMA were fightres are constantly grabbing, pulling and holding opponent, having superior grip strength and endurance is extremely important.
By manipulating how you hold the bar you can alter the way the exercise challenges your grip. BJJ black belt Dan Strauss shows you how to do it: