Reading over the full text of Essential Kill from Savage Spirits, we have this line: "When making a combat check that does not involve either using the Gunnery skill or operating a non-starship weapon, the character may..."
So ask yourself the following two questions:
- Does your attack use the Gunnery skill?
- Does your attack utilize a non-starship weapon?
If either of those is a "Yes" then the talent doesn't apply.
So, per RAW, it only works with weapons mounted on starships that do not use Gunnery...
I think that it should say "When making a combat check that does not involve either using the Gunnery skill or operating a starship/vehicle weapon, the character may...", but for those that insist on dogged RAW, this talent seems pretty useless.