I would like to collect some simple smart contract ideas (by simple I mean not Uber or Twitter ) in this thread that you would like to see and maybe someone will build it or will share an example like @bobert did with the Naive Lottery Contract.
It would be nice if you could provide a small use case as well, but this is not needed. Example:
Sending some amount to an address and it will be split (equally or by some sort of distribution key) to other addresses that are locked into the contract.
If the tip is very small it should keep the balance in the contract and distribute it later.