reverse grip, 90 degree angle knife ?

[pest-ilence]

I don't know where else to ask this so here it goes. I'm looking for a knife of a similar style to one I saw on TV. Its gripped in that hand with an ice pick type grip, the blade is the only oddly distinguishing feature. The fairly thin blade bends at a 90 degree angle back and runs behind your arm. It is used in a manner similar to punching, except for using the blade running along your arm. (I seem to remember something about tribal warfare in which machetes were used in this same, reverse grip punching motion)

Anyways could some one tell me what the as for mentioned knife is called?