Boorusphere - Yet another booru viewer for Android.
NeoDownloader - As you know, there is a lot of websites with a lot of pictures, music and movies.
Imgbrd-Grabber - Very customizable imageboard/booru browser and mass downloader, with powerful filenaming features.
WFDownloader App - A free bulk image downloader application that also serves as a multi-purpose bulk downloader for your PC.
Flexbooru - A booru client for Android, support Danbooru and Moebooru.
Transloader - Start downloads on your Macs, remotely from other devices