Here is my ideas of custom reports, which not presented in classic Magento reports.

So I have to realize time to time:

• Out of stock items vs Items in Wishlist
• Part of invoiced items (opposite un-invoiced)
• Quantity of buy items reflected on Marketing mechanic
• Payment system usage in case order on different regions
• RFM analyse versus Replenishment
• Promo Actions Calendar and selling prognosis

Do you have own? Write me below: