A dual sided mini ratchet with 1/4" and 3/8" drive sides. Total length is maybe 5". That combined with extensions in various lengths really increases my range. Would've improved my quality of life while replacing hard-to-reach fasteners holding an HVAC blend door actuator on my old car. What took me 3 hours and left me horribly bruised would be a walk-in-the park today.

I also love the Knipex plier-wrenches. The larger sizes open barely larger than 2"/50 mm, which is a huge help for some plumbing type work. My job no longer requires me to work on equipment with crazy uptime requirements, so now I use it occasionally at home.

Not this year, but I still love my stainless steel metric allen keys from Wera. The bodies are not hexagonal and thicker than the heads, so there isn't much flex. The head design isn't purely hexagonal, but designed so they never get stuck or damage bolt heads. I'd also consider the non-stainless versions - I needed the corrosion resistance when I bought them, but not any longer.