When all else fails, you can always resort to blunt force trauma. If you're out of ammunition, you'll have no choice but to take down a few Splicers with the wrench in search of loot. Combined with the Wrench Jockey and Wrench Lurker tonics, I suppose this weapon could make a good choice in certain situations or if you're looking for a bit of a challenge. Don't even bother trying to use it against a Big Daddy, though.

Your first opportunity to pick up this weapon will be shortly after leaving the bathysphere at the beginning of the Welcome to Rapture chapter.