One of my "main use" scripts is for shaft keyways. An input window pops up for selection and I choose a reference face, the cylinder the keyway is to be in, the offset of the key from the reference face, the key length, whether it has rounded or washed out ends and if it is imperial or metric and then press OK. The correct size key slot is created automatically. There is also the option for "non standard keys" which can be manually selected.
I have another one for internal keyways as well.
Another one reads diameter and distance values from an excel file and builds a shaft from it. We do a lot of multi stepped shafts. I can check overall lengths etc with the excel file before running the script. It helps to limit dyslexic finger mistakes.
Due to the programming involved, I think it's best to ask yourself, "What procedure would make my work easier if it was automated?" and go from there.
I've had help with nearly all my scripts from the python gurus here, but I got what I wanted in the end.