IT'S AN AUDIO RECORDER
I see very few people who take advantage of this one. I find it especially useful when someone is telling me something I need to remember, or need a record of. Video gets used a lot in place of audio, but it takes a lot more space, and its not always appropriate to have a camera in someones face. I use mine to record important phone calls, and I even like to ask permission to record, in case some legal issue comes up.