Accept "Colorado" and "Hoover"? (It might also pay to note that half of Lakes Mead and Tahoe, as well as half of Hoover Dam and Lake Mead, are in neighboring states)
The Sonoran desert definitely does not extend into Nevada. I've done the drive from Tucson a few times, and there is a pretty distinct transition as you leave the Sonoran desert on the way to Vegas.
Who fought Manny Paquiao? That's the best we could do for a question inherently about Nevada? I have several possibly topics infinitely more appropriate: nuclear testing, 'Battle Born', MGM fire, Binions/Rio home of World Series of Poker, McCarran Airport, other NV cities (Winnemucca, Elko), Reno's nickname, and any trivia about any of a dozen well-known casinos.
Worth mentioning that prostitution isn't legal is *all* of Nevada. It's legal in some counties, NOT all. Ironically enough, in Clark County (which includes Las Vegas), prostitution is illegal. Not that that stops massive amounts of sex tourism there.
I think there is some good Nevada stuff missing. The Killers are from Nevada, and it's where the Bundy standoff occurred. Some fun Vegas trivia is that Celine Dion has the highest-grossing Las Vegas residency in history. She actually has two separate residencies, which are #1 and 2 respectively. You could also use Reno's slogan, "The Biggest Little City in the World" alongside the Vegas quote.
(Or are you one of those who believes that athletic history is somehow "not culture"?)