Some ideas, mebbe:

  • Pressure points attacks to limit physical capability (reflected by Strength/Dexterity scores as well as movement speeds -- melee touch attack, which AC to target might be a little tricky).
  • Targeting the solar plexus to knocked the wind out of someone (save vs. exhausted/fatigued for one round/until taking a move/whatever action to catch one's breath).
  • A more extreme example of the above which borrows elements from Naturo and Avatar: the Last Airbender would be limiting spellcasting with the first option listed.
  • It's use is somewhat questionable, but you can control someone's movement to certain extent by pushing down on their clavicle. This tends to make people move down to avoid the pressure, which could be reflected as a trip attempt that offers no reversal opportunity and is opposed by a Will (or perhaps Fortitude) save instead of an opposed check.

That's all I've got for now. But in general areas that you might think of targeting with the somewhat-established called shot rule might make for reasonable skill tricks. The eyes for a one-round blindness, the groin for a temporary reduction to Strength/movement (maybe sickened for one round), etc.