Wrench Lurker

From BioShock Wiki

Wrench Lurker is a Combat Tonic which increases Wrench damage by 150% against unaware or shocked opponents and quietens the user's footsteps. It can be stacked with Wrench Lurker 2.

[edit] Game Caption

When fighting those stronger or faster than yourself, you'll need every advantage possible in a scrum. Wrench Lurker allows you to make the most of your opportunities when your antagonist is caught off guard.

[edit] Location

Located on the banister next to the Gene Bank in Neptune's Bounty, or can be purchased from a Gatherer's Garden in this area and onwards. Note: Picking up this Gene tonic causes Rose to appear and attack the player.