The long and the short of it

One thing about RuneQuest that gives it an edge over D&D is how it handles priority in combat. Rather than a more-or-less arbitrary initiative roll, it determined the order of attack by "strike rank" - primarily made up of weapon length and the character's reach (based on RQ's SIZ stat) and reflexes (DEX).

This is clearly explained in the RQ2 text:

A slow, small person with a long spear is still likely to get the jump on a large fast person using his fist. 

Surprise, movement and drawing weapons are also taken into account:

A fast, large man with a long weapon can be slow to react when a dwarf with a short sword and two heads steps out of the wall.  

All of this makes intuitive sense. In the D&D variants (as ever, I'm mainly thinking of Whitehack here), DEX - as the sole modifier of initiative rolls - has too much influence. There isn't a SIZ stat to compensate, though, so weapon length looks the obvious thing to consider when assessing "reach" (surely one of the most crucial concepts in combat).

A rough hierarchy of the typical D&D armoury might run something like this:

Spears
Other long polearms (halberds, guisarmes, bills, etc).
Two-handed swords, poleaxes, other two-handed axes
Long-bladed, single-handed swords (longswords, arming swords, rapiers, etc)
Short swords, one-handed axes, maces and warhammers
Daggers
Fists/grappling

When a melee ensures, I'm going to use this to determine who attacks first. Initiative rolls (and DEX modifiers) apply only in the case of a tie.

You might argue that a spear isn't necessarily longer than a halberd, and that a halberd has an effective thrusting point too. That's fair enough - but if used in that manner, a halberd would do no more damage than a spear and would also require two hands to use (it's not optimised for thrusting). So a halberdier can opt to use his weapon to thrust, counting as a spear , but will then do the same damage as a spear that round.

One thing I'm inclined to do is give two-handed weapons - including spears - a higher damage die. All weapons in Whitehack do 1d6 damage, though there are negative and positive modifiers (-1 for a shortsword, -2 for a dagger, +1 for a one-handed axe or sword or a polearm, +2 for a greatsword or battle axe, etc.). Negative modifiers don't reduce damage below 1.

I'm going to stick with 1d6 for most one-handed weapons (swords, spears, axes, maces, whatever). Shortswords lose out to longer weapons in attack priority, but do the same damage (gladiuses always look quite nasty to me). The advantage of a shortsword, of course, is that it's easier to climb or run with - and easier to conceal. And I think the same applies to daggers.

Weapons that can be wielded in one or two hands use a d8 when both hands are used (longswords - aka bastard swords - are the most obvious example here, but I'd apply it to spears too). This can't be combined with a shield, of course. Weapons that always require two hands - greatswords, poleaxes, halberds, etc. - use the d10. I prefer 1d8 to 1d6 +2 for a longsword wielded in two hands, because a big weapon can still cause a small wound.

These adaptations favour spears, which seems appropriate to me. Spears should have advantages in any game based on ancient or medieval warfare; swords were typically second-choice weapons. This system gives them a reach advantage that combines either with higher damage for two-handed use or a shield.

One further tweak I'm going to make is to apply a 'closing' rule for daggers, fists and grappling. Here's how it works. If a dagger-wielder is facing a spearman, the spearman attacks first. But if the dagger-wielder manages to wound his opponent, the dagger-wielder has priority in the subsequent round - and keeps it as long as he continues to draw blood. If he misses, the spearman restores range.

Finally, I'm inclined to make grappling rely on consecutive successes (I can't remember which game does this, but I recall that one does). So, your first success gives you a hold (and priority as with daggers above). your second success is a throw (d4 damage) and a third success gives you a pin. Specially trained characters can effect a lock or a choke on a fourth success. A character being grappled can continue to attack with a dagger or shortsword (or draw one), but longer weapons are rendered ineffective.