Thread downloader for some imageboards.
You can get the original (and outdated) application here: https://sourceforge.net/projects/ychan/
Windows & .NET 4.5 (Or WINE, for Linux. But I have not tested it on WINE. Yet.)
This supports a browser protocol ("ychanex:") for downloading through browsers. I included a very basic plugin for this (since I'm not very good at javascript it will not blend in too well) that adds a link on 4chan, 420chan, 7chan, 8chan, and u18chan (fchan is weird with their links). The protocol can be installed through the application (requires administrative permissions to install, it writes to the registry).