Bow hooks
Grunt tubes (I beat the true talkers up,but I really like their tone)
Tree steps,like Shultzy said you never have enough and I have a lot of them.
I sometimes forget things when washing clothing and drying out gear or transferring it from one pack to another,thats where the bow hookscome in,I just leave them in the trees until I take the stands down at the end of the season.
I have left behind grunt tubes,extra ammo,seat cushions,flash lights,knives,drag ropes.Gladly not all at the same time.