Steampunk.

[Reaper]

So would firefly/serenity be considered as steampunkery?

 

[ZOMBiiE]

I don't really think so because it's more sci-fi/western, it just doesn't have a very steam-punk feel to me. :S

 

[Trygon]

Far too high-tech for steampunk.

 

[Marble]

Firefly/Serenity would fit into the sci fi/western hybrids, as these fine gentlemen have said.