This could be one of the best Halloween stores in vegas. It is open year round, is packed to the gills with costumes, and the staff is friendly and helpful.
They are extremely busy this time of year, but the staff was willing to help answer my questions, help me find what I was looking for, and even opened the packages so I cold make sure the items would fit.
Their website is a great place to check and see if they have what you're looking for (they probably will). Besides costumes they also have a ton of decor and other spooky items to transform your house into the Haunted Halloween Digs you've been dreaming of.