http://www.youtube.com/watch?v=Ej3it7Ct76w&feature=related
Here is a video about it.
Im surprised it isn't in Zalanthas. Its so primitive...
http://www.zalanthas.org/gdb/index.php/topic,4565.0.html
http://www.zalanthas.org/gdb/index.php/topic,23331.0.html
http://www.zalanthas.org/gdb/index.php/topic,14872.0.html
There are a ton of threads that suggest atlatls, and I'm pretty sure they're confirmed for 2.arm. They're still awesome though.
mastercrafters get to work!