Android…
https://github.com/romannurik
https://github.com/skylot/jadx - Dex to Java decompiler
https://github.com/pxb1988/dex2jar - Tools to work with android .dex and java .class files
https://github.com/iBotPeaches/Apktool - A tool for reverse engineering Android apk files
https://github.com/java-decompiler/jd-gui - A standalone Java Decompiler GUI
https://github.com/google/android-classyshark - A tool to analyse your APK (Android app)