While I like a number of different versions of Catwoman and the Catwoman costume, I think my favorite will probably always be Michelle Pfeiffer's Catwoman from Batman Returns. It's that cooky Tim Burton design sensibility that just puts it over the edge.
And this is an excellent bit of cosplay. No, it's not a 100% faithful recreation of the costume but it is instantly recognizable
Source: Flickr - Soldatov Vladimir