Two thoughts. First, I don't know when you're driving but check for one-way specials in and out of PHX. When living in LAS we rented a Camaro convertible once for $5 a day to drive into PHX and spent a week doing the drive. We had a blast
Second, depending on how much time you have, for the LAS-PHX leg I'd suggest stopping at Hoover Dam (as others have mentioned) detouring to Grand Canyon, then stopping at Flagstaff and Sedona on the way down. Enjoy the trip!