Which of the free Vegas attractions and shows are must sees? Any opinions on attractions and shows that cost money and whether or not they are worth it?

Mystere at Treasure Island, worth every penny!

Free shows that are worth the time: Pirate Show at Treasure Island (almost getting to be NOT worth it with the crowds, see white tigers at Mirage, Volcano at Mirage, and fountains at Bellagio.

Pirate Show is worth it if you have kids with you, get there early. Fountains at the Bellagio is most impressive at night.

Definetly see the Fountain Shows at Bellagio... (beautiful) especially at night!!
Check out MYSTERE show at Treasure Island. Expensive but worth the money..
I hear "O" is a good show at Bellagio, but sells out fast.
We saw EFX at MGM hotel that's also a very nice show..
Have Fun!!!

The Mardi Gras show at the Rio.

Carrot Top (MGM Grand usually); Rida Rudner (NYNY) are great comedy shows at great prices; actually (don't laugh here) the Tournament of Kings @ Excalibur was quite good for only $30 per ticket; Lance Burton magic show at (Monte Carlo) at $60 was great; the "O" show is pricey (about $150 or so) but grand