Blackpowder
Horn or flask to hold it.
Powder measure
Flints or percussion caps
Round balls
Cotton patch material
Small screwdriver or nipple wrench
Hunting pouch (army surplus bags are great)
Cleaning jag
Ball puller
Vent pick or nipple pick (straightened paper clips or small feathers)
Oil
Options:
Lube other than saliva
Short starter
Cleaning patches (or, just use the same cotton as the patch material)
Black powder solvent (like water & Ivory Soap)
Ball block to hold pre-lubed patched balls
Nipple capper
Cow's knee (waxed leather to keep rain & snow off lock)
Mainspring vise (flintlock)
I also carry a small piece of 1" wide leather strapping for flint leathers & added purchsed when pulling the rammer (especially when pulling a ball). A shoelace and rolling hitch will do, also.
You can carry solvent or liquid lube in 1 oz spice bottles, and grease/wax lubes in candy/mint tins (burn the paint off & they look like old japaned tin).
A knife (or scissors) of some type to cut patches
A small pouch to carry the balls in
A priming horn or tiny flask if a flintlock
A bore mop to save having to cut a bunch of patches when cleaning
That's what I'm down to after 25 years of shooting. The father I get into it the less I lug around
Other nice items are a cleaning rod, a shot snake for smoothbores ( and wads and cards for same), a belly box/cartridge box for muskets, a dedicated patch knife on the hunting pouch, equipment to cast your own balls from scrap lead, a slip on sling for when the deer is down.