You do both damage and maneuver. Note that from a balance perspective, you are spending two actions (the current action and your next action) to do both damage and a maneuver, so you aren't getting a 'double action'; the stunt just lets you do the maneuver now instead of waiting, and lets you hijack the roll you already made. This is very similar to the Redirected Force stunt from Your Story, which lets you sacrifice your next action to use your current defense roll for both the defense it was intended and also a 'free' maneuver (which isn't really free since you're spending your next action to get the benefit).
Here's a rewording to clarify:
Force of a Locomotive, Size of a Breadbox: When you charge an opponent, you hit HARD. After a successful charge attack (ie, a successful tusk attack roll after having moved at least one zone) you inflict stress on your target as normal, and also may choose to sacrifice your next action (in the following exchange) to count the attack roll as a successful maneuver on your part (requiring no additional rolling), placing a maneuver aspect like Knocked Senseless or Ass Over Teakettle on your victim.
A question occured to me. For stunts like Redirected Force (and this new one) that require you to 'sacrifice your next action', do you think this implies sacrificing the entirety of your activity during the next exchange, or only your 'main action'. Obviously you can't to a main action like attack or maneuver, but can you still do a supplemental action like moving, do you think? On the one hand, supplemental actions are fairly innocuous, but on the other hand you 'pay' for the supplemental action by losing a die on your main action roll...
