Best one currently is ENS (Ethereum Name Service)
A decentralized domain name system for your wallet and contract addresses, no more copy and paste or using QR code.
Do you possess an ether wallet with your own private key, such as parity, mist, Trezor or Ledger Nano S?
Try and bid some names for yourself and understand how it all works, it's only 0.01 ETH for obscure names. And it's not really spent, just being locked away in smart contract until you release the name.
https://www.myetherwallet.com/#ensAnother very powerful usecase currently in production is actually online gambling, open to all nationality, races, ages, fairly simple to bet and 1% house edge.
Load this page with your mist, parity client or install the metamask chrome extension to interact with the dapp.
https://etheroll.comNext month, you can try out
Swarm cityEdit: one more thing, with dapps like Status and Token being able to communicate privately and transfer ERC20 tokens to each other, once you pair that with crypto debit cards such as Monaco, TokenCard and TenX, you can skip having a bank card for tiny purchase altogether