for me it really depends on what I am hunting, what time of year it is, and where I am...
if Im going to be sitting in a stand all day waiting on a deer near my home (southeast) during the first season (not too cold), all I need is something small and lightweight to hold some rain gear and other assorted items, maybe a snack and a water bottle, etc.. a small fanny pack works fine.. or often I just use my pockets..
If Im doing a hunt that requires me to move long distance, or carry more kit (elk in Colorado), etc.. I prefer a small day pack..
IMO the Kifiru Daystalker is about as good as it gets. It is pricey.. but its bombproof.. you cant tear it up even if you try.. its small and light enough not to be a nuisance.. but its large enough (about 1300 cubic inches) to fit everything you need for a full day in it, plus give you storage space if you need to stash a layer of clothes, etc.. its has plenty of pockets to keep your stuff organized.. and has some neat options you can order (customizeable) that you cant get with an off the shelf pack..
again, it aint cheap..
but its a pack that you buy once.. and will keep for the rest of your life.. you will not wear out the straps, the pack itself, etc.. like you will a $20 off brand pack from wal-mart..
http://www.kifaru.net/daystalker.html