I've made a few ring tones for the iPhone here and there. Then I tried to think of something cool. I thought it was funny during an episode of "The Good Wife" when the mother's ring tone blared her daughter's voice saying, "Pickup the phone!" Sadly, my friends and family wouldn't put themselves through the embarrassment of recording their voices.
Why not use a computer's voice? So, here I am, making custom ring tones using Text Edit, Automator (not sure how else to get text to speech to save to a file on Mac OSuX Tiger), and Garage Band to create ring tones. I use a brief introduction tone, then have the computer speak. "Incoming call from: ..."
And now I'm downloading the sound files of characters speaking in Portal to perhaps use them as ring tones.