There will never be a singular killer app for crypto. Just like there isn't a killer app for USD or Gold. It is the aggregate adoption, as a transfer of value, across numerous use cases that makes any currency valued.
1. A way for businesses that cannot get a bank account to accept digital payments. Think porn sites or marijuana stores.
2. It's used on darknet markets for obvious reasons.
3. You can use it to pay for things even without a bank account.
4. Send money to anyone from anywhere.
5. It can be used as a decentralized timestamping service[0].
6. Lower fees than other digital payments (credit cards take 1-4% fee per transaction, plus other costs).
Cryptokitties is just like Beanie Babies and in my opinion not very interesting.
[0]: https://whycryptocurrencies.com/timestamping_service.html
Yes. Sending censorship resistant transactions.
If you look at crypto, you will see that it has, in general, for whatever reason, been censored less often than things like bank or credit card transactions.