Well, judging by the number of exclamation points you put, im guessing you need it open rather quickly
The quickest way would be the trusty ole' crowbar. A hammer would also do the trick. Or.. both
If time isn't much of a concern to you, then you could learn to pick it. It's only a wafer lock so it won't be hard, or very time consuming. If you dont' wish to buy lockpicks, you can use simple paperclips or pins, and some kind of improvised tension wrench.
If your going to learn to pick ive provided some helpful links below:
Steve Hampton's Guide =
http://lockpicking.i8.com/(ebook)%20Illustrated%20Secrets%20of%20Lockpicking.pdf
MIT Guide =http://www.gregmiller.net/locks/mitguide/
Both are very helpful, but if your going to learn only wafer picking, then you should read Steve's guide, it talks more about wafers.