One of the coolest areas on earth for me is Vegas and, more particularly in Vegas, the Mandalay Bay. The Mandalay Bay Resort & Casino is more than a hotel.. it is a little piece of heaven with its own tropical paradise where you find a wave pool with real sand, a lazy river which you ride along lying on rafts and even a beach casino (where, unlike normal casinos, casual dressing is highly welcomed! :). I heard that concerts on this beach club are amazing at night too and just in case you were looking for more spicy activities: they now have a Shark Reef Aquarium, a sort of giant aquarium with giant rays, piranha, golden crocodile.. where you can dive with sharks!! I recently tried it in Dubai (in the fantastic Atlantis hotel which also provides this sort of dive.. and it was one of the best experience in my life (but more on this later!).
Make sure you check out this hotel and in case you (or your friends) still think that Vegas is only for poker players, check out this guide which explains all the other things you can do in the city of Vegas. Cause there is no place like Vegas!