I've rented from several places at VGT (N Las Vegas) and the place I would recommend in West Air. Good aircaft, good attitude. Grand Canyon West is owned and run by Hualapi Indians, hence the charge if you don't take the tour. They're very friendly and may waive the fee if you go to the gift shop and buy something.
Going further west to Grand Canyon central is good, but it's 6500' high and gets very cold. Land there, get a cab to the rim of the canyon and pay the driver to stay there to collect you. He'll probably give you a tour as well. Just make sure the weather is good, it's not very forgiving around there.
Going further west to Sedona to see the red rocks or to monument Valley is also good, but in a 172 it's definately an overnighter.
Make sure you see the Hoover dam, but keep your eyes peeled. You won't be the only aircraft circling it!
Another good destiantion is Furnace Creek in death Valley. At 250' below sea level, it is the opposite of Grand Canyon Central. The valley is spectacular and there's a good visitors centre there. You will have to pay the standard $10 for every vehicle that enters the National park as a landing fee, but it's worth it. Take tie downs though, the winds pick up in the afternoon and aircaft have bben blown over there.
Taxi drivers will take you to VGT, the FBO can call you a cab to get you back. but it's a long way and pricey. So like s many destiantions in the US, it may be a good idea to hire a car.
Have fun!