CLI aficionados working on any of the many *nix platforms are likely familiar with at least a few of the types of pipes available for creating powerful one-liners to get things done. One idiom I find particularly interesting is that used by the RVM installation process.
$ bash < <(curl -s https://raw.github.com/wayneeseguin/rvm/master/binscripts/rvm-installer)
In one line, the script is both downloaded and executed without ever needing to be written to disk. Recently, Justin Kulesza and I have been working on setting up some new virtual machines using Puppet. Needing to quickly bootstrap the process, installing the Puppet dependencies and setting the system time, we decided to adopt the above idiom for our bootstrapping script.