my daypack is a shoulder bag (unfortunately most of my outings these days are only a beach trip with my little friend Biscuit (a dog) and take only about 2.5 hours... occasionally i'm visiting a friend who has a jungle property but the set-up in this case remains the same) which contains:
fire kit, pocket camera, small container (originally from some japanese energy drink) with some bandaids, some dunny paper, cheap p38 can opener copy and some fish hooks + a bit of line, small bag with 10m 5mms rapelling cord, titanium spoon (found brand-new), roll of electrical tape, small japanese waterstone, pair of surgical rubber gloves (first aid item before someone asks...)and a piece of orange marker tape, small torch,some cordage and since 2weeks again a pocketboy
, sometimes also a "silva mini ranger"
hopefully one day a monocular as well....
if it looks like it's raining i'll wrap a lightweight rainjacket around my waist, water is usually not carried around here as i can manage that long without water or grab a coconut but i've a 500ml stainless steel bottle i can carry on a shoulder strap and another one i can hang from my belt
in northern Australia i carried my 1qt canteen (+A.D.F. cup) in a PLCE pouch (+second canteen if needed) as well, using a webbing belt with Y-harness (== less sweaty than a backpack) when i went a few hours bushbashing or fishing
if i know i'm out for a full day i put my shoulder bag inside my daypack (a "tatonka" daypack i've since 2006), together with notebook, poncho, head torch, larger FAK and maybe a snack
several sharp items and a walking stick are usually with me as well