I'll second the recommendation for Nine Fine Irishmen in the New York, New York complex. Downstairs amongst the slot machines... It can be a challenge to locate. I went there for dinner on my wedding day in May (kilted of course!). Pretty standard fare, but the atmosphere is wonderful, the food good and the waitresses barely dressed ;-)

Besides that, I enjoyed the Fremont Street Experience much more that the mega-hotels on the new strip. Much more relaxed. There is a Hennesy's there, which makes for a nice place to relax and have a pint or 2 and watch the people go by. I also went there Kilted. Heck, I was kilted most of my week there.