These have been in the game for almost 9 years and they have not one purpose. They're not used in any quest or synthesis recipe. Please give these a purpose. Please don't relegate these to the same fate as Nidhogg Scales which also had no purpose until SE made it used in a worthless synthesis recipe for a piece of furniture nobody cares about.
Some suggestions for Cactuar Needles:
- Some Needle Crossbow Bolts.
- Needle Arrows.
- A high level spiked mace or staff.
But if this idea is ever forwarded to the developers I bet they'll end up making Cactuar Needles used for a lame Jumbo Cactuar statue furniture piece. =(