OnionShare permits anonymous file sharing through the TOR browser, eliminating the need for third-party file sharing apps.
This app is quite simple to use, open up TOR (this action provides the Tor service that OnionShare uses to start the Onion service) and then drag n' drop your target file into OnionShare and click start sharing. It will then produce a unique .onion URL that can be shared with specific friends, coworkers, etc. The recipient doesn't even need to have OnionShare on their machine either; they only need to open the URL you sent to them in Tor Browser to be able to download the anonymous/secret file.
Once the file has been downloaded by the selected recipient(s), OnionShare will automatically cease sharing it; this feature is set by default. But you can allow for multiple downloads by changing the setting.