I lived there for about 12 years. Depends on what you like. And they keep adding and changing some things yearly.
The strip is it. Las Vegas Blvd. From around Treasure Island to the Luxor. Ceasars is a great casino/site to visit, as is most around there. The mirage with the volcano, treasure island with outdoor pirate attacks, bellaggio with one huge fantastic fountain show, the rolller coaster at NYNY, the island at the tropicana, the MGM has a huge indoor amusement park and many fun things, Ballys has maybe the best show, jubilee.
Between the strip and downtown is the Stratasphere. That is a must. Go to the top, you can see all Vegas and the surrounding mountains. I'd go at night to see the lights, and at daytime to see the mountains. At the top they have some killer rides that will test your manliness. You will have to see to believe. I dare ya.
Go to visitor centers and look for funpaks. They give you discounts on about everything. Sometimes free meals.
Not much downtown. But if you go, go at night. They have it enclosed and a huge lasar show. Between 11pm-7am the horseshoe has a NY strip steak dinner for $2.
For gambling, remember how nice those hotels and casinos look. They get that way by people losing.

You can play something like nickel or quarter poker all day and get free drinks. Anytime you gamble, you can get free drinks. They want you to be 'relaxed', so you lose.
It's fun walking through the larger casinos and seeing all the sites. Some have hammerhead sharks, dolphins, all kinds of neat things.
Out of vegas is hoover dam. You can tour the inside and it's a decent tour. Bad thing is you can no longer get to the place where you can take the best pic. They blocked it off fearing a terrorist attack.
There's also red rock canyon. Bring dog food for the wild donkeys. If they are still there. Valley of fire is a very neat place. many movies were filmed there. But it's 70 miles from vegas. You can take some real cool pics there though.
There are many grand canyon tours from vegas. That place is the most awesome sight I've ever seen.
More later....any questions, just ask.
