Depends on your likes. My brother and I have been going to LV for years, and we have done quite a few non mainstream things. I would agree with the previous suggestions of the Hoover Dam and the Grand Canyon. That said, you can get a coach tour to these, if you don't have a car. Until this year, we have not rented a car in our previous 18 annual trips. We have either used public transportation, or taken a tour.
A favorite place of ours has been the Pinball Hall of Fame. It is a huge location with probably close to a hundred pinball games of all eras that you can play. Cost per game is anywhere from $0.25 to $0.75, depending on the age of the game. Its a great way to pass a few hours, and is easy to get to via the bus.
Other places of interest might be the Springs Preserve, the Clark County Museum, the Las Vegas Zoo, the Atomic Testing Museum and the Marjorie Barrick Natural History Museum. almost 5 years ago
some unique, not mainstream suggestions for Las Vegas.Compared with other cities in the western U.S., Las Vegas (literally, "the springs" in Spanish) is a relatively recent arrival. It was founded in 1905, and for many years it was merely a small settlement in the middle of the desert. However, several pivotal events would come together in less than twenty years that would help Las Vegas grow into what it is today: about 4 years ago