[3.5 & PF] small using medium weapons

[JeenLeen]

I know there's the general -2 penalty for using an oversized weapon, but is there any rule in PF or 3.5 that states that some medium weapons count as a different weapon if wielded by small characters?

For example, is a medium dagger a small shortsword?
I didn't see these rulings when I looked at the open source stuff online, but I thought I read such somewhere. (In particular, our party found a +1 Keen Longsword, and my small gnome ranger is the best one to use it, but I really don't want that -2 to hit.)

I'm most interested in Pathfinder, but curious about 3.5 as well.

Side Questions related to Size: if a small PC wields a medium arrow as a dagger, it would count as oversized so you'd get the -2 penalty, right?
The ammunition for bows is of different sizes, correct? For example, a small bow uses small arrows and a medium bow uses medium arrows. I wanted to make sure the different damage die comes from the arrow size, not just the bow size.

[Hunter Noventa]

A medium dagger is NOT a small shortsword, even though they otherwise have the same damage profiles. It's kind of silly.

But basically there's no built-in way to do it. Pathfinder lacks a weapon enchantment that allows a magic weapon to resize to it's wielder, and I don't know of any feat that allows for what you're trying to do.

Though a feat that negated the penalty doesn't seem like it would be too broken. You'd still have to use two hands to wield that +1 Longsword for example, but you'd be better off with a Small Greatsword (which does 1d10 damage as opposed to the longsword's 1d8)

As for the arrows I'm not sure, I'd presume it's a combination of the two, but a smaller bow would have smaller arrows.

[Diarmuid]

This mentality is a throwback to how 3.0 treated weapon sizes and is not represented in 3.5 or PF.

[Slipperychicken]

A dagger is constructed much differently than a shortsword, and an arrowhead differently than a dagger, so I'd say it doesn't work that way.