The father of a close friend of mine was a design engineer with Lockheed back in the 60's. He's in his mid 80's now, still uses a slide rule and hates calculators....
My dad had me memorize the base 10 log tables. Helps me calculate interest rates at the car dealership, and is good for parties, where I calculate the 17th root of number in my head, to a digit or so. Also useful in calculating odds in poker.