Initiative and Weapon Size

In Original D&D and similar retro clone RPGs the weapons all roll the same dice to see how effective they are in combat: one six-sided die. While I like the simplicity of this, I've always felt this gave little incentive to use larger weapons. Why carry a Great Sword when a dagger is just as good? Why spend money on a Battle Axe when a wooden club is every bit as effective?

This led to all sorts of new rules over the years where weapons do varying amounts of damage (a rule I still like), affected different types of armour in different ways (which makes sense… but fiddly), or had different speed factors affecting initiative (again, logical but very fiddly).

Here's a simple rule for weapons in an RPG.

Longer weapons make attack rolls before shorter weapons.
Weapons of equivalent length roll for initiative.
But since we don't want everyone to now run around in tiny winding corridors with ridiculously long polearms, we'll also include this rule:
Close quarters
Combat in narrow hallways, stair cases, thick forest / jungle, or other crowded spaces reverse the initiative order: shorter weapons make attack rolls before longer ones. Additionally any long two-handed weapons (Polearms and Great Swords) can not be used effectively and can only attack once every 2nd round.
They're still dangerous weapons, but they aren't as fast as something smaller and more wieldy in a confined space.

Even relatively unobstructed locations can have close quarter areas. Clever players will choose where to stand and fight to benefit their choice of weapon.