The Duck Shop
Forced to be called the Duck Shop because it's NOT affiliated with , the Duck Shop is the place for quality overpriced Duke merchandise of any kind. With everything from apparel to lawn chairs to shot glasses to pretty little pictures, the Duck shop has it all. If however, you are on a tight budget, I recommend the union's cheaper (by sometimes $20) apparel, or going to the Bryan Center on West for more options.
Note: you may want to get there early in the term to buy things, as the good sizes usually sell out.