There are some proposal such as CoinJoin which proposed by Gregory Maxwell, even though this idea isn't perfect and without proper feature upgrade/implementation, it will leaks users info. Some coin such as DASH already use CoinJoin, but many people say the implementation was done badly.
But, i think Bulletproof's proposal is better when users need privacy
![Roll Eyes](https://bitcointalk.org/Smileys/default/rolleyes.gif)
More info :
https://bitcointalk.org/index.php?topic=279249