Im going to have to say a power adder. I love the look of a big turbo hanging out of a fog light hole, a procharger inlet box coming up from the intercoolers, or a bottle or 3 hangin out in my backseat
Id say wheels, but not all fbods need new ones to look good. SS 10 spokes and iroc wheels were great. On the other hand, just about everything in between were pretty aweful.