The Gerber Fiscars Sport Saw. Scarey sharp, feather light, and retractable. I drilled a hole in the back for a paracord lanyard.
Yep, that's the one.
Since there's a newer model out, I'm holding out for a sale. Then every kit gets one of these.
EDIT: But avoid this turkey like the plague: http://www.mec.ca/Products/product_detail.jsp?PRODUCT%3C%3Eprd_id=845524442626997&FOLDER%3C%3Efolder_id=2534374302696925#tab3
(MEC is simply awesome; but on this occasion they've been 'had.')