Transparent voting mechanisms, prediction markets, p2p betting, gaming micropayments, distributed computing rewards, replacing entire national currencies because of irresponsible governments,etc
Distributed computing rewards - maybe for a subgroup off applications (eg. illegal stuff eg. piracy), but in general terms a centralised system is easier, cheaper and quicker to develop
Replacing national currencies - this is already bitcoin's killer app. Ethereum adds almost no utility to this space.