Dr. Farrell is a scientist and has been given the title Sir for his works.
Upon defeating him, you could get any 3 or 4 of the following:
Aurora Shield (1)
Aurora Shield (2)
Random Level 20 Weapon EXP Boost 4 (Level 17) Weapon Enhancement Powder Armor Enhancement Powder Farrell's Jewel Dr. Farrell Gloves
The Gloves are the most coveted by people, mostly BM/Aco. You could sell them for 60g [Adv]