I pick up trips every couple of months in LAS and when I go I do a hotel/rental car deal. The best deal is about $50, which gets you a night at Circus Circus and a rental car at Dollar. I know everyone will say that Circus Circus is awful, but they just remodeled the West Tower and the rooms are better than most hotels I have ever been in. For May I had to pay an extra $5 to stay in the West Tower, but worth every penny.

FYI I have noticed in May it was $71 for a night at the Luxor and a rental car. So don't just limit yourself to a hotel when getting a rental car and hotel package may be a better deal.