Shuf

shuf is a command-line utility included in the textutils package of GNU Core Utilities for creating a standard output consisting of random permutations of the input.
The version of codice_1 bundled in GNU coreutils was written by Paul Eggert. It is not a part of POSIX.
Example.
$ ls
Wikibooks Wikipedia Wiktionary
$ # Shuffles input 
$ ls | shuf 
Wikipedia
Wiktionary
Wikibooks
$ # Picks one random line from input
$ ls | shuf -n1
Wikipedia