Below are perl one liners I have written. I write them for fun, when challenged to, or when bored.

perl grep (like unix's grep utility) - example args: '^[Cc]hris[^:]*' /etc/passwd

perl -MFile::Slurp -we'$;=shift;print+grep{/$;/}read_file(pop)'

portscanner

perl -MIO::Socket -wle'map { IO::Socket::INET->new(qq($ARGV[0]:$_)) and print } 1..$ARGV[1]||10000' localhost 1000

Fetch a webpage (text-mode)

perl -MLWP::Simple -wlegetprint+shift 'http://site.com'

Generate random alphanumerical string (password generator)

perl -le'print map { (a..z,A..Z,0..9)[rand 62] } 0..pop' 7


Have a better/similar/smaller solution? E-mail me the one liner and I will put it up (and give you credit).