Kangaroos in the Wild
Kangaroos do punch, and they do it with devastating ferocity. Kangaroo fighting, often called boxing due to its resemblance to human boxing, is done mainly as a way to establish a dominant male in a troop of kangaroos. The 'roos will rear up on their tail and hind legs and swipe and punch at an opponent's face and chest, aiming for eyes, ears and nose, and may even grasp onto them to inflict more damage with an exponentially more powerful hind-legged kick.
Kangaroos vs. Humans
Kangaroos have also been known to attack humans, especially when a mother feels that her joey is threatened or in the case of a rabid kangaroo. Severe lacerations and cuts can result from being punched by a kangaroo. Your best bet is to leave the animal alone and not go near it, members of its mob or its babies. Though there is some debate as to whether kangaroos are actually territorial or not, seemingly unprovoked attacks can be the result of treading too close to a herd.
Self-Defense
When threatened, kangaroos will mostly just run away. They can run upwards of 30 miles an hour and leap more than 30 feet in one bound. However, when cornered, they will not hesitate to resort to pugilism to defend themselves. In defense, kangaroos will claw at a predator's face and eyes, but will mainly stick to using the haymaking kicks of their hind legs, which are powerful enough to easily disembowel most animals.
Protecting Yourself
If you feel threatened by a kangaroo, your best bet is to get away quickly. Run away from the kangaroo and away from any members of its mob. Cover your face and turn your front side away from the 'roo to protect your vital organs. If you are actually struck by a kangaroo, call for help immediately. Make noise and run toward other people. The 'roo will often back off and let you be after you leave it alone. Seek medical help immediately if you are cut.