Military members and veterans can signup for an upgraded military rewards card that gives free parking at MGM Resort hotels. Other hotels, like Cosmopolitan have free parking for hotel guests. Wynn and Encore are free for registered guests. Luckily, some major Vegas hotels, like Rio Suites, Treasure Island, Tropicana, Rio Suites, Stratosphere, Circus Circus, are still free for everyone. Most of the hotels offer an hour of free parking.
Below is a list of the major Las Vegas hotels and what they charge for parking. The parking fee rules are complicated and have certain exceptions, such as local residents and Rewards Card members getting free parking. This is in addition to the mandatory Resort Fees. Unfortunately, this benefit is quickly changing with many hotels now charging them. Not that long ago, one of the nice Vegas perks that almost all hotels offered was free parking.