This is a great whistle very similar to many whistles available from places like REI or Eastern Mountain Sports. Its is compact, since rather than using a cork ball, it simply uses air. It is cheap and only requires a bic pen. It also makes a great addition to survival kits, such as the Altoid Survival Kits found on Instructables. (See link.) This is my first instructable, so I decided to start with something simple. Please drop me a comment.
www.instructables.com/id/Pocket-sized-survival-kit/ (by LinuxH4x0r)
(Note: This is a very loud whistle and a knife is used to make it. I am not responsible for any injury caused by using this whistle)
Also: If you know what lockerz is, view my other instructable for an invite. If you don't, please, look at my other instructable, it's awesome.