I think that one of the most amazing reports that used data is the "Arsenal Global" from The Intercept Brasil. In this work, the journalists walked around the Rio de Janeiro's streets to find lost bullets and find out where they came from. They found bullets that came from another countries and in some cases the bullets were from prohibiten lots in Brazil. The places where they walked to collect the bullets were shooting zones, so it means that what they found could say something about the origin of the shoots that killed many people,could be from police or drug ealers.
I like this report because besides they building the data, the journalists also searched for official sources using the LAI, so it has quality. I think it's a great report for study data journalism.