Instantly turn a car into a Tardis, Land Speeder, or NCC-1701
Geeky stick-on car emblems turn Pontiac Aztecs into AT-ATs and AMC Gremlins into Galacticas.

I'm against tacky faux chrome stick-on portholes on cars, but I wholly endorse Etsy seller Empira's geeky custom car emblems.
The emblems cover most of the top sci-fi franchises, including "Star Wars," "Star Trek," "Battlestar Galactica," "Doctor Who," and "Firefly." There are even shout-outs to the fictional Canyonero from "The Simpsons" and to Atari with an Atari 2600 stick-on.
The emblems are convincingly done in the style of real car emblems. The Land Speeder even apes the look of the Land Rover logo. If you already own a vintage Ford Falcon, then you'll be on top of the universe with a Falcon Millennium Edition stick-on. Prices range for $12 to $15.
The most believable car emblem of the bunch is obviously the Tardis, since a Tardis that has a working chameleon circuit can look like anything it wants to. I'm thinking this would be a good addition to my Prius, which already has chrome V8 emblems and a Miskatonic University parking sticker.
(Via The Mary Sue)