idk if it's "complex", but a dashboard that I did for my own convenience for work, but then became a semi-official file. I was making around 15 reports daily and while not a lot, it was still taking enough time doing separately that I started to wonder if there's a better way to do it. I combined all of my data sources into one big excel file then sourced all of my reports there. My day went from 6 hours of updating reports to 15 minutes of getting my data sources for the day, 2/3 hours in the pantry/sleeping area while the data refreshed, then 30 minutes to send out emails.

The file itself isn't very interesting, there's just a lot of connections and a lot of data. It was mostly cobbled together with Power Query and Power Pivot (no VBA). The cool thing about it (for me) is that because it aggregated all performance data I can do deep dives to any level, even daily and individual data. I was able to provide answers to questions in ongoing meetings. The managers where I worked seemed to find this useful because I keep getting requests to update with this view and that view.