Only the Oxford English Dictionary app comes to mind, terrible (content aside, hence managing to retain “killer” status) and ugly as it is.
However, it in no way stands as example of either good design or the strengths of Flash.
grooveshark.
Grooveshark has an HTML5 version now, im pretty sure
Last time I checked - actually yesterday - the HTML5 is only used for the UI part. The audio is still done in Flash, maybe for the sake of DRM. I hate it, because I have my Flash plugin removed. I have to open Chrome just to use Grooveshark.