I tried to add this to the old thread from last year, but it was closed. They just opened a new smoking lounge (plastic cage) in C concourse. It is kind of hidden, close to gate C5. This is easily accessible to the A and B gates without going through security (lots of walking though). They have one in the D concourse, and also one in the new T3. This has to make Mccarran one of the most smoking friendly airports in the country. No matter what gate you are departing from, you now have options without going back out through security.