Well, the Notes app on Mavericks uses Core Data. I know it's a trivial example but it's the first one I found. (~/Library/Containers/com.apple.Notes/Data/Notes

Well, the Notes app on Mavericks uses Core Data. I know it's a trivial example but it's the first one I found. (~/Library/Containers/com.apple.Notes/Data/Notes/NotesV2.storedata is a Core Data SQLite store.)