Shark Reef is amazing, Lawrys is pretty insane as well - I used to work across the street from there and we would hit the lunch menu once in a while. If you can, sometimes there are courtesy shuttles from the airport to the Red Rock casino, way up on the west side of town. There is a BBQ place there called the Salt Lick that is pretty good as well. Across Charleston from the Red Rock is a place called Islands. REALLY good burgers.
Like I tell everyone, Vegas is great for about 3 days. After that you run out of things to do.