The approach of Brendan, and the commenters on G+, is to create small mechanical benefits of various kinds for the different weapons. I don't belittle that at all, and I love some of the ideas, but on the other hand the purity of all weapons doing apparently the same amount of damage is appealing to me.
I find myself increasingly wondering whether there needs to be any explicit mechanical differentiation between weapons given that different weapon types provide in-game benefits outside of combat for an enterprising DM and players. Viz:
- Daggers are concealable. This is a particularly useful attribute if the DM is being sensible about social rules and not just handwaving the fact that players are wandering around the local nobleman's palace or merrie olde inn armed to the teeth with awl-pikes, tridents and spiked chains.
- Polearms, spears and their ilk are useful for probing and measuring. They are an invaluable dungeoneering tool. This is why all 1st level fighters should have a spear or similar as their primary weapon.
- Axes can be used to hack down doors and other obstacles.
- Slings are essentially infinitely re-loadable provided there are rocks in the vicinity. They can also be used to hurl flasks of oil.
This makes me think that every kind of weapon can provide a benefit of some kind without violating the d6 for damage standard or even introducing any mechanical difference. Even two-handed weapons could be seen as intimidating and factored into the DM's calculations for how potential foes react to the PCs.
I'm coming around more and more to the view that good gaming is about the DM paying careful attention to the details of his world to the extent that the players are aware that every choice they make has consequences. This seems to feed into that philosophy.