If you had to choose just one...

[santaman2000]

-Tropical or semitropical environment: a small machete

-Temperate climates: something a bit heavier; a smallish Bowie, an MOD knife, a Puma White Hunter type knife, etc

-Plains climate: same as temperate, likewise for a desert climate, and a mountain climate

Coastal/beach climate: this ones a bit harder to narrow down to a single knife as coastal environments differ around the world but I'd want a stainless blade here (probably both a filleting knife and a shucking knife)

 

[SGL70]

This works for me:

 

[Dave]

Knife, mmmmm dunno. Whatevers available, but if it was a choice of just one tool, Id take my dave budd hawk, which Ive become quite attached to. You can do a lot with it.

 

[MartiniDave]

It would have to be my trusty old WS Micarta Woodlore. The best all-rounder I own, second choice my Helle Eggen,being a stick tang it's not quite as robust as the Woodlore, but the edge retention is fantastic.

 

[John Fenna]

Well - if we are talking on TOOL then it would be my GB SFA ....

 

[woof]

Bernie Garland recurve bushcrafter.

Rob

 

[ammo]

Chris Caine survival tool. If only allowed one tool, ill go with a machete. Chops, carves, digs a hole, clears an area. The most versitile wilderness tool. If allowed other tools, then it would have to be the Skookum or Stuart Marsh. bushcrafter.
If only allowed one, i certainly wouldnt carry a stick tang knife. I agree that they are better balanced, more comfortable and so on, but any full tang knife is a stronger safer, more reliable option.