Most of the blackpowder weapons available today require a primer of some sort. Some use a #11 nipple (I think), mine uses a 209 shotgun primer. While I can make or find the black powder and mold the bullets or balls, those primers are necessary to fire the weapon.
A flintlock would be nice but the prices are rediculously high. So, I stock 209 primers and figure that I'll have something with which to obtain something better.
PVC pipe, a little glue, and a BBQ igniter will make a dandy weapon without any powder, primers, or bullets. I once made one that would fire a raquetball and of course there is the traditional potato. Of course there is always the bow and arrow, crossbows, slingshots.... there will always be some weapon available that will fire a projectile.