I love themes, so last year, we went as a hydrant (poor husband), dalmation and fireman.
The hydrant costume was my own design. I worked roughly off a simplicity pattern for the fireman costume, but modified it to look just like my husband's real bunker gear (he plays a firefighter in real life). My costume is more of a reconstruction with goodwill and lots of black felt. The only store bought item is my son's helmet.