For some reason, I can't think of much to add right now. Trust me, there's tons of things I've done that I wouldn't recommend, so I'll be sure to update this list as I think of things.
Hotels: Anything downtown that wasn’t mentioned above, Stratosphere, Tropicana, Imperial Palace. I used to hate Wynn based on my experience with the hotel during its opening weekend, however I stayed again in February, 2009 and had an AMAZING stay. It's now one of my favorite places to stay in Vegas.
Restaurants: Prime (Bellagio) (overpriced for quality), Hugo’s Cellar (used to be much better, gone downhill, especially the service), the major chain restaurants (treat yourself to something unique to Vegas or something they don’t have in your city/state)
Buffets: Bellagio, Fremont, Palms, Sahara
1. Planet Hollywood