Let's never stop improving smart contracts security best practices. The winner of #USCC is invited to Lyon, France! http://u.solidity.cc/

The 1st Underhanded Solidity Coding Contest :

The Underhanded Solidity Coding Contest is a contest to write harmless looking Solidity code that conceals a hidden purpose. A good USCC entry looks like a clearly and straightforwardly written smart contract, but contains well disguised vulnerabilities that ensure its actual operation differs significantly from what the reader would expect. The USCC is inspired by the similar Underhanded C Coding Contest.

http://iex.ec/?p=1218