On Sun, 27 Sep 2009 18:00:15 -0600, rw
wrote:

I'll say a favorite fly box full of your favorite flies for your
favorite water. Store-bought flies, self-tied flies, friend's flies --
productive flies that you have confidence in, even if you don't know the
names or remember the lineage of most of them.

Anything else can be replaced with a lot of money and a little trouble.

Did exactly that last month on the upper Brazos, just below Whitney
Dam. Got caught in a strainer on my 'yak, and lost not only my fly
box, but my eyeglasses as well. :-( MUCH more upset about the
glasses, as I had paid $325 to have new lenses put in my favorite old
frames just 6 months prior. I have since fixed the problem of losing
the flies: I keep all my gear in an Orvis Safe Passage Sling Pack.
Keeps everything handy, but safe and out of the way until I want it.