I think it's perhaps called a "Pana" in the Philippines. However, Google doesn't turn it up on "Pana," and I'm not sure what the real name is. I got this from a guy in the US who's selling something similar.
"Pana" link
Basically, it's a single band slingshot (i.e. a stick with a large rubber band attached), with a loop on the end of the rubber. The dart is hooked to the end of the rubber, stretched out, and fired. Not really a crossbow, just an outgrowth of our modern elastic technology.
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