The Ranger (Hunter) in my group would like some variety in his arrows. I didn't want to get to complicated so I tried to keep it simple.
Piercers: piercers are made for penetrating heavy armor. The heads are narrow and do not cause the trauma that arrows with broader heads do. Reduce the die type by 1 (d8 becomes d6). Lower the AC of medium armor by 1 and lower heavy AC by 2.
Broad head: These arrows are broader than standard arrow heads. Most commonly used for hunting they sometimes have use in battle.
Broad head arrows cause slashing damage rather than piercing. Raise the damage type by 1 (d6 becomes d8). Raise the AC by 1 on all targets.
Bladed: These arrows are more utility than weapon. Shapes range from fan to "U" shaped. Bladed arrows do slashing damage. Bladed arrows get a +2 for hitting small (none combat) targets and trick shots. +2 to all AC vs Bladed arrows.
Thumper: also called stun arrows used as a utility arrow or none lethal alternative. Thumper arrows do 1d4 bludgeon damage. Target hit by a thumper must make a Con save vs 10 (15 for called shot to the head) On a failed save the target is disadvanyaged till the beginning of its next turn. On a save roll of 4 or less the target is stunned.
This is still a work in progress. I need to play test and work out the math a bit more, especially the thumper save. I had the idea to do barbed arrows that would do damage when trying to remove it. But couldn't think of a simple way I liked.