Sometimes it's quite difficult to keep on top of all the new features that we implement. One I had missed that I just found out about yesterday, goes all the way back to 9.1, when we got advisory locks with transactionaly scope. These locks work just like the normal Postgres locks, in that they go away when the transaction in which they are obtained commits or rolls back, and they can't be released prior to that.
What makes this so cool is that it makes these locks a whole lot safer to use. I'll be looking to use them now in places where I haven't previously used advisory locks, because making sure you release the older style advisory locks in all the possible code paths can sometimes be quite tricky, and getting it wrong can have nasty consequences.