My list, based on my experience, Las Vegas reviews and overall popularity.
Best show in Vegas, in my opinion
4. Danny Gans at Mirage: UPDATE: Danny Gans passed away earlier this year. It's too bad, he was a wonderful entertainer and a real mench. He contributed to just about every charity in Vegas and really went above and beyond for this community. He will be missed. :(
5. Comedy Stop at Tropicana: UPDATE: Closed. Just wasn't popular enough, unfortunately.
-Other popular comedy shows- The Improv Show at Town Square and Bonkerz Comedy Club at Palace Station--both off the strip. Harrah's also has a comedy show that receives good reviews.
6. Blue Man Group
-I'm not a huge fan of this show, but it's pretty popular here.
7. Spamalot: UPDATE: Closed and is no longer in Vegas.
If you like Monte Python, this is supposed to be good
8. Lion King
I have yet to see this show, but it's supposed to be AMAZING.
-DH loved it, I didn't. More story line than other Cirque shows. Great theatre/stage
-It's ok. More sexual than other shows, not suitable for families.
Fantastic, especially if you love the Beatles. Even if you don't, the show is a wonderful way to spend an evening. The show room is perfect, giving all seats a great view. The show is entertaining and the music is wonderful, even for this non Beatles lover!
-Best Venues--Hard Rock (pool, joint), Mandalay Beach (stage is in the water), House of Blues (Mandalay), Lake Las Vegas (concerts on the water at Montelago)
13. Live Music Venues
-Nine Fine Irishmen (Irish bar in NYNY with awesome Irish band, dancing), Fremont Street (not always, but pretty often), NY NY Piano Bar (also one at Southpoint and Golden Nugget, but this is the best), Champagne Bar at Paris