When making homebrew weapons, interesting weapon features are an asset. So here are three I came up with, and the weapon I came up with them for:
1. Super-exotic. A weapon with this property is considered exotic for purposes of proficiency. It is, however, far rarer than most exotic weapons, and unless in an area where it is commonly used it is not available for sale in shops. It may, however, be crafted on commission at 5 times the normal price. (The masterwork price is multiplied in the same manner, but costs for a magic weapon are not.) A character crafting such a weapon for himself pays half the listed (normal) price, as though it were a regular exotic weapon, but the craft DC is 20 rather than 18.
A character with the racial ability to treat a super-exotic weapon as martial may begin with such a weapon (or more than one if he so desires), using its normal price. Any other character must spend 5 times the normal price to begin with the weapon.
If a projectile weapon has the super-exotic property, so does its ammunition (unless the ammunition is used for a weapon without the property as well.)
2. Weak. A weapon with this property is usually extremely small, and has great difficulty dealing damage. A huge weapon with this property does 1d2 damage, which then proceeds to increase with size as normal (so the weapon does damage as a shuriken 2 sizes smaller). A small, medium, or large weapon with this property does only 1 damage.
In addition, most forms of damage increase do not apply to the weapon. The weapon (if a melee or thrown weapon) grants no bonus damage from a high Strength score, and cannot deal critical hits. If made into a magical weapon, it gains bonuses to the attack roll as normal, but no bonuses to its damage. It cannot do any type of precision damage, including critical hits. It also cannot gain any property that allows it to do ability damage (such as the Wounding property) or untyped bonus damage (such as the Merciful property). It can gain elemental damage effects (such as Flaming or Frost) but always does minimum damage with the resulting bonus dice. It can also gain alignment-based damage-granting effects (such as Holy or Anarchic), but the bonus damage applies only against targets with a subtype opposed to the weapon (so a weak Holy weapon would do 2d6 bonus damage against demons, but not against most evil creatures.) Weapons with this property are usually used for poison delivery.
3. Quick. A weapon with this property is extremely quick to use. It is a move action to attack with such a weapon, and a character making a full attack with it is entitled with one bonus attack; this stacks with all similar effects. If a projectile weapon, reloading the weapon is a free action. For balance reasons, any weapon with this property should also have a substantial liability, such as the Weak property.
And now for the weapon: Blowgun (this replaces the version in the DMG). A blowgun is a Super-Exotic Weak Quick weapon, with a cost of 1gp and 1gp for 20 needles (before the multiplier for a Super-Exotic weapon). It has a range increment of 10', and a weight of 2 lbs. (The needles have no significant weight).