Survival:
A stillsuit.
Please don't anybody tell me that they don't know what I'm banging on about...
I can't say that the thought of surviving on my own (or anyone else's for that matter) recycled body fluids appeals overly, but if the balloon ever did go up it would no doubt come in very handy...
Camping:
A single pill that grants a lifetime's immunity to Scottish midges with no side effects
Bushcraft:
The means to visit with our paleo ancestors (and return in one piece) to understand how it actually
is done when it's a full-time occupation...