Where are you coming from? For Phoenix there are shuttle services from several parts of the state. I would do that and leave the car at home if possible. Or bum a ride and take the driver to dinner and pay for a hotel room (depending on time of year you could get a good deal in LAS)

Edit: Also price out two one way car rentals to see if that would be cheaper, or a car rental one way and ride the other way. One way car rentals into PHX can sometimes be very cheap in February because the cars are needed for spring training.

7 years... <clapclapclap>