Arizona, the "Grand Canyon State", is named after its main attraction – the Grand Canyon. It really is worth a visit if one is close by – which means, by US standards, within 1000 kilometers.
I visited Arizona while doing a tour of California in 2003. The main focus was, of course, on the Grand Canyon. However, this US state also has other things to offer: The Historic Route 66, for example, is very popular among bikers. Even when going by car, it offers a nice distraction from the long drive between Las Vegas and the Grand Canyon.