Ghostbuster costumes, like many others, tend to evolve over time. So far I've built a proton pack and Ecto goggles.
Update: Dragon*Con 2011 pic:
Here I am actually wearing it (right before DragonCon 2008):
In 2009 I marched with the "PKE Surge" Ghostbusters contingent in the DragonCon Parade. We even got a pic on the CNN website. Yep, that's me behind the guy with the hat.