Rhumbar is a good place to go and get a drink (Get a big one! They are expensive, but they are refillable and you get a discount on the refill!), and lounge outside on a nice night. They have about 5 different flavors of frozen drinks to choose from, and 5 different glass sizes/shapes. The drinks are STRONG, so you do get your money's worth.
Outside there are flat screen TV's, heat lamps, nice couches and chairs to lounge on, a few bars, waitresses to wait on you, and hookah! You also have a decent view of Treasure Island's show at night. It's a good place to come and chill.