CDisplay Ex - CDisplay Ex is the most used comic book reader.
Boorusphere - Yet another booru viewer for Android.
YACReader - Download YACReader for your platform. Windows, Linux, MacOSX. And enjoy you comic books cbr cbz with the best comic reader.
Imgbrd-Grabber - Very customizable imageboard/booru browser and mass downloader, with powerful filenaming features.
Tachiyomi - A free and open source manga reader for Android.
LoliSnatcher - A booru client with support for batch downloading, written in Dart/Flutter for Android but may support more platforms in the future.