Great breakfast and open 24 hours!
I've stayed at the MGM Grand multiple times and always end up going to Avenue 24 at least once if not multiple times throughout the stay. I've been here most often for breakfast and they do a damn fine job of curing the Vegas hangover - or at least fueling you up for the next round. Service has always been really good here, they get you seated fairly quickly even when it looks packed and the wait staff is very attentive to any of your needs.
Good menu selection, reasonably priced, and a relaxed atmosphere make this a great place right in the middle of it all at the MGM Grand.