Also known as cattle bars or bull bars, their original purpose (before they became a trendy embarrassment for urban posers) was to protect the front of your truck and radiator if you collided with a cow. In the apocalypse, there are no cows, because zombies ate them all. Zombies are the new cows.
Make sure it has a winch, too
Just in case your car gets stuck somewhere, you'll need a way to get yourself out. Provided there aren't 30 hungry creepers descending on your cerebellum at that moment in time, a winch is an invaluable tool.