A debilitation and targeted magic spell. Two contests.
1) TM to hit and do damage
2) Debilitation to determine the secondary affect of the spell.
It would require 2-3 spell slots and probably 250+ ranks of each to use effectively.

Debilitation Effects:
Arms/hands - if successful they drop what they're holding in that hand.
Chest/Back/Abdomen - if successful it knocks the target back to pole/missile depending on how successful
Head/Eyes - Causes a stun
Legs - causes them to kneel/fall depending on how successful.

Pre-reqs would be TKS and Mental Blast.