In 2007, Valve Software released Portal, one of the most enjoyable and creative video games of the year.
But you already know that.
I have created a custom voice file for GPS units with a stylized voice in the fashion of GLaDOS, the charmingly creepy antagonist of the game. That's right. You can now dutifully follow directions from your GPS unit all the while wondering if the next instruction will lead you to your GPS-planned doom in a car wash retrofitted with flame throwers and sawmill blades. Take a look at the video below for a very quick sample of the voice.
Update: Distribution of the GLaGPS voice is now being handled by PigTones (Politcally Incorrect GPS). In addition to the voice file as well as a number of other high-quality GPS voices, there is also a simple installer available for Garmin devices.