I had a second-hand HP-35 when the 65 came out. I was programming desk calculators. The 65 looked better. I talked my roommate into buying one.
Calculator Floating-Point using 0-7 of the ten digit display to work out conversions into and out of CDC floating-point representation.
Road Rally Calculator which told the two-time winning team exactly how we weren't going to win a third time.
See other Handheld Calculators