I'm not quite clear on the question. Are you saying knives and pocket tools are excluded? Define "survival situation". Wilderness or city? Hot or cold?

I'd second a PLB. Or a cell phone. Or a FAK. Or a Bic lighter. Depending on the situation. If knives are allowed, maybe a OHT. Or a phasor. Yeah, a phasor would cover a lot of bases.

Kevin B.