Can 'Not So Fast' counter the ability of 'Zaun Punk'?

Ruling: Yes, you can use 'Not So Fast' to counter the triggered ability of 'Zaun Punk' if your opponent chooses your gear as the target.

Nuances:

• 'Not So Fast' checks what target is actually chosen, not whether the card text explicitly says 'friendly'
• If the opponent chooses your gear, it becomes an enemy ability choosing a friendly gear, which meets the criteria for 'Not So Fast'
• The additional cost paid to trigger the ability (killing a friendly gear) cannot be countered and remains paid
• If the opponent chooses their own gear, 'Not So Fast' cannot counter it since it would not be targeting a friendly gear