Geolocation is a good example. HTML5 is going to get a geolocation API that works just beautifully even on devices with no GPS. Flash based applications will (currently) only get access to geolocation APIs when targeting the AIR runtime on mobile. Some browsers (I only know of Firefox 3.5 on Mac and the WebKit browser on the Nexus One) already support the HTML5 geolocation API… So why not use that to get geo information into your Flash based application?
There are few things I love more than geography and by extension, geolocation. It’s the digital overlay of the world. How can that not be cool? And this particular example is nice because it’s an area where HTML5 is ahead of Flash Player. Just like HTML can use Flash to implement ideas it hasn’t nailed down yet, Flash can use HTML to implement ideas that it hasn’t got yet. Bliss.