I want to escalate the social pressure on @ekzyis to make some progress on his prediction markets website. It's a very neat idea and fills a very valuable niche in the bitcoin/lightning ecosystem. As far as I know, the main player providing that service right now is freebitcoin. If you followed that link, you can immediately appreciate how much room there is for improvement.
I'm most excited about sports and politics predictions, personally. There are other ideas being kicked around in the saloon today that are quite exciting too: I'm particularly drawn to being able to make predictions about news stories (perhaps whether something turns out to be a hoax) and court cases.
What kinds of prediction markets are other people excited about?