leetCrypt.scala

object	LeetCrypt
{
	implicit class Encrypt( src:String )
	{
		def leetOfString( s:String ) = {
			s.map(
				c => c match {
					case 'a' | 'A'	=> '4'
					case 'b'	=> '6'
					case 'B'	=> '8'
					case 'e' | 'E'	=> '3'
					case 'g'	=> '9'
					case 'l' | 'L'	=> '1'
					case 'o' | 'O'	=> '0'
					case 's' | 'S'	=> '5'
					case 't' | 'T'	=> '7'
					case _		=> c
				}
			)
		}

		def stringOfLeet( s:String ) = {
			s.map(
				c => c match {
					case '4'	=> 'a'
					case '6'	=> 'b'
					case '8'	=> 'B'
					case '3'	=> 'e'
					case '9'	=> 'g'
					case '1'	=> 'l'
					case '0'	=> 'o'
					case '5'	=> 's'
					case '7'	=> 't'
					case _		=> c
				}
			)
		}

		def toLeet	= leetOfString( src )
		def fromLeet	= stringOfLeet( src )
	}

	def main( av:Array[String] ) = {
		lazy val crypt	= av(0).toLeet
		lazy val origin	= crypt.fromLeet

		av.size match {
			case 1	=>
				println( "L33t:    " + crypt )
				println( "Plain:   " + origin )
			case _	=>
				println( "Please give one argument to encrypt/decrypt" )
		}
	}
}

Very basic l33t convertor, in Scala
Damn, I love Scala <3