Advanced Black-Red Hawkeye Crystal

Which one? Ah, it's a base mod in a few blasters:
Quiet
Precision Strike
Peace
Overkill

And some Lightsabers:
Echo of XoXaan
Heart of Ragnos
Oath of Ragnos

These crystals can be ripped from the following weapons:

Battlemaster PVP weapons (Battlemaster PVP vendors, 1,550 Warzone Commendations each)
1) Battlemaster Force-Master's Lightsaber
2) Battlemaster Survivor's Double-bladed Lightsaber
3) Battlemaster Vindicator's Lightsaber
4) Battlemaster War Leader's Lightsaber

Rakata PVE weapons (Rakata vendors).
1) Blood of Korriban (1 Unassembled Rakata Master Force Mainhand Weapon)
2) Echo of XoXaan (1 Unassembled Rakata Master Force Mainhand Weapon)
3) Darth Sion's Lightsaber (1 Unassembled Rakata Frontline Mainhand Weapon)
4) The Heart of Ragnos (1 Unassembled Rakata Frontline Mainhand Weapon)
5) The Oath of Ragnos (1 Unassembled Rakata Frontline Offhand Weapon)