I have had this discussion with a few outfitters. Here is what I have come up with.
I tip the outfitter 10%. He can distribute it as he sees fit among his staff. I then tip any particular individuals that I feel went above and beyond my expectations, whether it be the guide, the cook, the wrangler or whatever. I have given away a few knives, but it has always been as an additional gift, not in lieu of cash. Knives are great gifts, but they the don't pay the bills.
Likewise, in some foreign countries, in addition to cash, I have left behind clothes and boots which always seem to be appreciated.
donsm70
