UPDATE: Folks have pointed me to a few sites like this that offer this service already. The quality of the voices are a little short of professional, but some (like the Governator, Arnold) are pretty darn funny.

It's time has come - a manufacturer finally created a voice-themed GPS device, this one using KITT from the 80's Knight Rider TV show.
>>It was bound to happen sooner or later: Generation X nostalgia and modern technology have come together in the “Knight Rider” Global Positioning System from Mio Technology.
The Knight Rider GPS (www.knightridergps.com) takes both its sound and style from the 1980s television show about a computerized talking 1982 Pontiac Firebird named KITT. William Daniels, the actor who was the voice of the sleek black car, narrates the unit’s driving directions. The device, which sports a black exterior and flashing red lights, can be personalized to use one of 300 common names in the greetings and random phrases it utters.<<
Who's going to be the first smart entrepreneur to apply the mobile world paradigm of downloadable ringtones to GPS voices?
There's bound to be a market for everything from Shrek's voice and expressions ("You are dumber than a donkey! I said turn left!") to Yoda directions ("Left you will go, young padwan. There is no try, just do").
More entrepreneurial types will of course recognize the potential for, ahem, adult-themed directions as voiced by their favorite screen stars ("Oh you are a bad boy, I said to turn left ...").