I think one of the coolest things to have multiples of is high end shaving brushes. You hear about Simpson Super and Manchurian, Plisson HMW, Rooney Finest, Thater 2 band and wonder what the fuss is about. Get different brands with maybe different style handles, lofts, knot diameters, and you'll find out what the fuss is about, and also determine what your preferences really are in a brush. With brushes you don't know till you try.