Pinotage said:
Can you use a two-handed weapon in one hand? So, for example, can a fighter wield a glaive in one hand and take a -4 penalty, or can it not be done at all?
It can't be done at all. Unless it's a lance, and you're mounted.
Also, how do weapon sizes work with ranged weapons? What size bow can a small character use and what are the penalties for using different size bows?
As written, a Small character can wield a Colossal bow, at a -10 penalty.
The penalty is -2 per size category difference between the character and the weapon.
It's an oversight in the rules. A Light weapon a size larger is treated as a One-Handed weapon; a One-Handed weapon a size larger is treated as a Two-Handed weapon; and a Two-Handed weapon a size larger is treated as a larger-than-Two-Handed weapon. A weapon that changes to something other than Light, One-Handed, or Two-Handed cannot be wielded.
However, those designations only apply to melee weapons. So a bow - even though it requires two hands to use - is not, in fact, a Two-Handed weapon. Or a Light weapon, or a One-Handed weapon. So when you use a bow a size larger, it doesn't
change to something other than Light, One-Handed, or Two-Handed - it was never any of those in the first place! So the rule doesn't prevent you using that bow. Or the bow two sizes larger. Or, indeed, the bow five sizes larger.
I asked Customer Service about this when 3.5 first came out; they suggested a possible house rule: you can only use a ranged weapon up to two sizes larger or smaller. So a halfling could use a Diminutive or Large bow at -4, or a Tiny or Medium bow at -2, or a Small bow at no penalty, but not a Fine bow, or a Huge or larger bow.
But it's up to your DM if he wants to implement some sort of house rule - that one or another - or none at all.
-Hyp.