What to take?

[Allan]

No one has mentioned an item that I always carry, just in case, and that is a good metal whistle.

[Ed_D]

No one mentioned either a stringer or a camera, because if you don't bring back fish or pictures of fish, no one is going to believe you caught any, especially any big ones. A little first aid kit is a handy thing to have, just try not to have to use it. Waterproof enclosures for cameras and/or cell phones are also a good idea, even if you are not planning on getting wet, sometimes it happens, trust me I know.

Consider the Betty Hiner "There are no trout(s) in South Dakota" gambit with regard t stringers and cameras. Betty is attempting to employ a part of the "blue line" ethos on an epic scale. You know the deal. "There are no fish in this stream. I only fish here to enjoy the scenery. Trying to catch fish here is a waste of your time." And for extreme cases there is the, "and besides, the moonshiner/pot grower//meth brewer in the cabin beside the stream shoots all strangers." There's just enough chance of that being true to dissuade a lot of folks.

I double bag, usually with Ziploc freezer bags, my wallet, and cell phone. My camera is guaranteed to a water depth of 10 feet. Ziploc freezer bags are tougher than their sandwich bags.

[narcodog]

Stored the vest away about five years ago, I just use a lanyard. On the lanyard I have a pair of Dr. Slick 4 1/2 in pliers, C&F combo tool, nippers, threader and eye cleaning needle. I also have a bottle Frogs Fanny and fake amadou. Small LED flashlight two spools of tippet material, usually 5x and something else. Two small fly boxes, one will be a nymph box, emerger box or midge. The other will be a multi compartment box for flies of the day.
Then I carry a water bottle on my belt along with my Folstaf stick and my instanet. If I am going to be hiking for a distance and away from the truck I'll carry extra drink, cheese crackers, power bar and if needed a rain parka. Very light weight, no strain on my neck or back.

[BigA]

I fit all of this in an old Patagonia vest pack.

Tippet Spools (2 to 4 depending upon where I am fishing)
Fly Boxes (2 to 3)
Platypus Water Bottle
Scissors/Hemostat combo
Nipper
Split Shot
Floatant
Indicators
Tape Measure
Tiny Flashlight
Hook File
Small Compass
Waterproof Camera
Cliff Bar
Dried Figs in Zip Lock Bag
Waterproof bag for phone and keys
Leaders
Small Kleenex Pack
Tiny disposable lighter wrapped in plastic
Rain Parka if necessary
Swiss Army Knife in my pocket

[holensum]

ditto, except for the flashlight, shot and thermometer. I fish during the daylight hours, have lead or beads on the flies and and know the water is cold . Oh and 2 boxes of flies, wets (nymphs, streamers and wet) and dry, both with various sizes and colors.

An excellent question. Beside the obvious of way too many boxes of flies:

Polarized sunglasses
Flashlight
Nippers (on a zinger which also functions as a tape measure)
Spools of tippet material 3x - 7x
Paste floatant
Powder floatant/drier
Shot
Hemostat or fine tipped needle nose pliers
Ketchum Release tool
Fishing License
Thermometer

[CaseyP]

frankly, not too much. gave up the vest the day one autumn when i cleaned it out and found TWO full water bottles...wondered why it was heavy.

now use a lanyard, pockets, and stuff hanging off the belt--net, stick. look sort of like an odd Christmas tree, but no weight on the shoulders!

[vicrider]

I only fish in daylight too but the flashlight should be in there anyway. Otherwise yeah, all that good stuff but...NO BOBBERS...