Easy - anything boring. "Boring" usually means repetitive and not mentally challenging, which to my mind is exactly what computers are for.
Even if the task happens infrequently and the script takes longer than the task, automating it is worth the investment:
- It prevents having to remember or re-discover how to handle the task next time.
- It ensures the task is handled consistently.
- It prevents potential manual errors.
For example, on the financial side, my company runs bank accounts in five countries, each with different GST/VAT taxes. Over time, I've developed scripts that grab the mid-month exchange rates that our Internal Revenue service requires to be used; crunches downloaded bank transaction data into categories (including tax inclusion or not); and exports it all into a huge Google spreadsheet. This provides global and country balance sheets and profit and loss, and when tax reporting time comes for each country, a tab on the spreadsheet provides all the figures so filling returns is a five minute process. Occasionally the scripts will flag an unrecognised transaction, and rather than manually correcting this in the spreadsheet, I'll add a rule to the script so it is recognised next time.
Cumulatively this probably took several tens of hours to code, but it means we don't need to employ an accounts clerk. It takes about fifteen minutes a month to download the bank data (manually - oh how I wish banks had APIs) and run the scripts. Our accountant loves this - the spreadsheet is shared with him, he can check our formulae or add other metrics, and he prepares our annual report an order of magnitude faster than any of his other clients.