Tiny sample:
Laptops need small USB flash drives so they don't get knocked off, but the caps are easy to lose. Solution - one big cap of normal thumb drive size, with room for three small drives. I call mine home, work, and share.
Ships' propellers are sized for clearance in harbour. If they deployed a larger one in deeper water, they would get > 20% better mileage. The more water you push on, the less it is running away from you. Marine architects have been using the Betz limit instead of the Froude equations, even though it is clearly misapplied and giving "impossible" results. My test boats won races right away.
Windmills would go in faster and cheaper with guy wires up the tower as far as possible. That goes double for offshore towers.
Undersea generators should be on moorings, not posts. That way they can fly to the bottom to clear shipping, and to the surface for service, with much lower installation cost.
A land vehicle should carry more than it weighs. Most of a car is hauling image and fear, not physical needs. I built one using controlled flex in the frame to give fine suspension without all the separate parts used now.
"Self driving" should begin with just controlled-access express lanes, with cars, trucks, and delivery robots automatically assembled into almost-touching trains in perfect safety. You just engage the system at an entrance ramp to get slotted into a passing gap, and punch in your exit. Vehicles could recharge, and drivers relax. One lane does the work of many, and reduces wind resistance losses.