Dirt Simple Weapon Dice

Every weapon gets its damage die size from its properties. Start all weapons at d2, this is the damage all improvised weapons deal. Then increase the die's size by one for each of the below that is true. I stole the basic concept for these rules from Unknown Armies weapon rules.

Melee Weapons

Sharp or penetrating?
Heavy enough to crack bones?

Long as your arm or could be wielded easily with both hands?

Daggers, Blackjacks, Quarterstaves are d4

Swords, Spears, Spiked Maces, Axes are d6

Battleaxe, Warpick, Glaives are d8

Ranged Weapons

Sharp or penetrating?

Does the projectile move faster then a human could throw it?

Heavy enough to crack bones?

Is the projectile OR launcher as long as your arm?

Slings and Darts are d4

Javelins, Hunting Bows, Hurled Boulders are d6

Longbows, Ballista, Cannonballs are d8

Spiked Trebuchet Balls (siege weapons) are d10

Uses

By using this method, it allows for an easy way to figure out the damage for improvised and non-standard weapons. Whips for example would be d4, since they are longer then your arm but not inherently sharp. Bladed whips would be d6. Adding spikes to a mace increases its damage.

Enhanced Weapons

Each of the above qualities that is enhanced beyond 'normal' for its material give the weapon +1. I should mention here I dislike the idea of casters 'enchanting' everything, since it takes away conceptual balance and makes the setting too caster-centric. Just note that being beyond 'normal' can be done through rare materials, enhanced crafting techniques, and pouring in your blood, sweat, and tears. Everyone is 'magic' in my game, don't make a discrepancy.

Sharp enough to cut through lesser metals, or blade cuts through flesh like butter? +1

The weapon is super dense or adds momentum to its swing? +1

The weapon can extend its range, or is incredibly well balanced? +1

The maximum bonus a weapon can have from regular enhancement would therefore be +3 for melee. I suppose ranged could be up to +4, but most DMs don't go around handing out magic catapults. Any other enchantment to the weapons would require something specific, like a flaming brand, the weakness of a monster, touch of a divine being, etc. Normal magic weapon stuff.