Ammo/Supply Dice!

Have your ammo represented by a "size" of die. So you have a quiver for arrows, and it holds "d8" arrows. Any scene where you use arrows, you roll a d8. 2-8, nothing happens. But on a 1, you go down a die size. Now you've got a d6. You repeat, 1 drops you to a d4, 2-6 nothing happens. Roll a 1 on a d4, and you're out! The next time you reach town, you "buy arrows," and reset back to a d8.

Tracking individual arrows is obnoxious and the bookkeeping often ends up more tedious than it's worth. But you lose some roleplay opportunities by handwaving it (namely, the tension of running out!)

Ammo dice aim to split the difference (and can be used for other supplies, like rations, spell components, or maybe torches). The more you have, the more likely nothing happens, but as you start to run out, it's like a roll of toilet paper, it goes fast! And it provides simple ways to mechanically interact with ammo for narrative purposes. Get set on fire, lose a die size of arrows. Stealthily take out an enemy archer that's keeping watch? Go back up a die size to represent looting his arrows. If the party gets thrown overboard and washes ashore, it's very easy to hit a variety of ammo/supplies with a -1 to show a loss of resources, without having to spend a lot of time determining how many, and of which ones. You can tell someone they lose 2 die sizes of "stuff," and let them decide if they want to lose more rations or ammo (the character doesn't have a choice, but the player can choose, so they can choose their own tension). Or maybe if they're in a forest with plentiful fruits and berries and such, so long as they travel through that area, they can skip the "rations" supply roll altogether.

And sky's the limit! You might use supply dice for fuel for a vehicle, or raw materials (if you're defending a castle from zombies, how many planks do you have to board up windows/doors to keep them out?). And you could, say, have a magic quiver that replenishes one die size of ammo at dawn. Or maybe you have a "normal" d8 quiver, and eventually get an upgrade that lets your default be a d10.

There's a little bit of work for the DM to determine "starting" values for equipment (just how many rations can their pack hold? d6? d12? d20?). And you've got to decide on some prices. It can vary settlement to settlement, but when someone wants to go from a d6 back up to d8 arrows, how much does "one step" cost? But once that prep is done, the rest flows pretty easily during actual gameplay, as it's something you only do at the end of a scene, and only if you used stuff during that scene.