A weaker Morrigans Javelins special attack effect every once in a while.
Pretty much the bleeding effect, but since they only hit around 30 ish, it would be significantly weaker. Also, this would make pvm a lot easier, and provide a use for the now-useless Barbed Bolts.

Sorry bubbles
I just remembered that this was a thing:
http://emps-world.net/forum/index.php?topic=4792.msg36442#msg36442
It would be nice to see them have a good spec so they could be "slayer bolts" or give 5% more exp alongside the other stuffs (slayer helm, boots, gloves ...)
Even more awesome would be an entire set dedicated to the skill (why not the constructor clothes that atm useless?) imo for every form of combat and would then we could have a universal armour that would be kinda weak, slightly better than dragon, weaker than barrows. but that would be too much.
E.g. The entire set could combine the exp given up to ~33% more exp changing its cost to more slayer points
:3

I agree that barbed bolt-tips are rather useless yet common drops atm. should be changed.