My husband loves Halloween and we usually hit all the costume stores in the area atleast once. Even if we don't buy anything, we still have fun looking around.
The 50% Off Card Shop always has TONS of costumes, decorations, party ware, toys, goodies and accessories. We bought my son's pirate hat, hook and eye patch here last year for less than $5 total.
They have costumes for every member of the family, including naughty and nice costumes for adults. My husband always tries to get me one of the naughty costumes, but that's a different story.
Excellent selection and a wide variety of sizes, including plus sizes. Prices are affordable too. Lots of fun and scary items!