Rent a fancy car in both places. Return the car to LA and fly to LV and rent another fun car. Avoid

Several of the rental chains: Hertz, hotel accommodation Avis, National, Budget offer fun cars from some of their Southern California locations. You will have to do your web site work to search availability and convenience to your stay.
The best place to start to answer this question is at Kayak.com , which allows to search several URLs for one-way car rentals. You can also specify the class of car you want -- luxury, premium, or convertible.
I was easily able to find several hotel accommodation of the above car classes for a one-way, one-day rental between these two cities for about $200. The key is to pick it up right as you're leaving for Vegas, and then drop it off in Vegas before 24 hours have transpired.
Since a car is a car, and Hotwire only lists the biggest name brands, it generally doesn't matter from which company you get a luxury car, as long as it's a luxury car. Note, however, that you give your money to Hotwire when you make the reservation, and you can never get it back -- you pay for the car even if you never make the trip.
What ar eyou actualy looking for? there ae companies that rent luxury and specialty cars - although don;t know if you can return to a differnt location. You can easily get a Rolls or a Bently or a Ferrari or whatever - but be prepared for very high rates. (I'm not aware that regular rental companies have these available.)
If you want to find the best deal on car-rentals by going, one site at a time, to Hertz, Avis, Thrifty, Alamo, Fox, National, Enterprise, Payless, RentaWreck, Budget, EZ, Advantage, Discovery, Midway, Dollar, etc, etc, etc; fine. I'd rather have someone do that for me, particularly since Kayak does it for free and in a matter of seconds. I thus find only the rental companies that have (1) an office close to where I want a car, (2) an office that's open at the time I want to start or end a rental, (3) the type of car or rental policy I'm looking for, and (4) a price much better than others. This saves a LOT of time. And, because Kayak checks car companies I'm not even aware of, I might also save a lot of money.
One great feature hotel accommodation of Kayak is that it allows hotel accommodation me to enter one search criterion, after which Kayak does the same search on its competitors' URL. I can then check out Hotwire or Expedia or Priceline or CarRentals (any combination, including none) with only one entry. If one of Kayak's competitors finds a much better deal than Kayak, I go to that site for a closer look.
I've tried other sites -- Travelocity, Hotels.com , Orbitz -- and I use Hotwire and Priceline on occasion. But I keep coming back to Kayak. If there's a better site, I'd love to hear about it. And, until someone does tell me about a better hotel accommodation site, I'll conclude I'm completely justified in calling Kayak the best.
Rent a fancy car in both places. Return the car to LA and fly to LV and rent another fun car. Avoid driving I-15 from Victorville to Las Vegas. The Mojave is not that interesting even in the daylight.