An ultrasonic parts washer to clean up old carbs for barn find cars that haven't run in 25 years. And, in addition to an impact driver, possibly a couple of cordless drills with different bits, Torx, Phillips, etc. pre-installed, so one doesn't have to waste time changing bits.
And, in an ideal world, two or more tool chests, so that all tools have their individual drawers, labeled with the tool name. An inexpensive Brother label maker can usually be picked up at Costco, Sam's Club and Office Depot for around $30.00, and the labels look so much more professional than those labeled with a black Sharpie on a piece of masking or duct tape. And the label maker can always be used for dozens of things around the house, too.
Also, pre-planning the job, and setting out all the tools that could be possibly needed for the job, and keep them within arm's reach, rather than having to get up and search for them in the tool chest, making for a quicker job.