My always & every time list
Everytime I go hunting, solo at least 75% of the time, I carry a lighter, T.P., a backup knife, a compass, a whistle, a flashlight and about 50 feet of riser cord.
A) The lighter is obvious, just make sure you don't get one that will crap out if it gets wet.
B) T.P. serves as "strikin' paper" and as a decent fire starter if you roll it up and fold it in on itself. Light the center and it will burn long enough to light tinder.
C) The backup knife is to take care of camp chores, should I have to camp. Primary knife stays sharp. If I have to camp, I have to skin & eat game.
D) Compass is also obvious, just pay attention to your directions going in or they'll be meaningless to follow out.
E) Whistle to tell everyone my pitiful butt is lost, please come rescue me.
F) Flashlight also self explanatory. Put batteries in backward until needed. They won't go dead that way.
G) Riser cord is also called 550 cord. If you're ever stuck in the boonies you're gonna wish you had rope. This is small, strong and easy to pack.
Other stuff will vary by location and weather conditions. Wet? Extra socks. Sunny but snowy? Sunglasses. You get the idea. A first aid kit isn't a bad idea. I confess to not carrying one, that will probably change when I get hurt.