another suggestion for sourcing ideas is to identify weaknesses in popular products then build something where that weakness becomes a strength (e.g., browsing in smartphones => iphone, search in portals => google).

re the unsexy filter, success can create sexiness. nike sells shoes. amazon sells books. salesforce sells enterprise software. yet these are all considered cool, sexy companies for the most part. if you build something people love, you can make it sexy. worry less about if something is sexy today, and worry more about building something people will love tomorrow. sexiness will follow.