The Kindle seems like a very versatile machine. It's not just for books, but to me, a near all-around replacement to printing things for personal use, and more importantly, a gateway to content that I'd never otherwise see.
Of course, with such a versatile device, there must be many unique uses for it. So what's the most unique thing you use your Kindle for?
For me, sometimes I have a (growing) collection of my favorite songs' lyrics on my Kindle. There's something to reading the lyrics instead of listening to the song or playing the words in your head. I'm not sure what it is.