Vegas is all about indulging your every whim and fantasy. Best advice: wear the most outrageous stuff you feel comfortable in. Dress a little flashier. And throw some money around. I tried doing Vegas on the cheap once. What a stupid idea that was. It's all about spending money.
So - go for stuff that's flashy and nightclubby. For nighttime, something pronounced and spicy. Don't know your wardrobe or budget, but something in the Serge Lutens oriental realm would work. Body Kouros maybe, at a lower spend level.
Daytime: the usual rule would be fresh or citrus, and you'll do fine with something like Mugler. But it's Vegas, you know. Never known for being especially tasteful. So wear whatever you like. In a town where it's considered normal to be smash drunk at any time day or night, you won't shock anybody by wearing the wrong cologne.