MakeAppIcon - MakeAppIcon resizes and optimizes your icon designs into all formats needed for iOS and Android mobile app!
Radix Icons - A crisp set of 15×15 icons. Open source.
EasyAppIcon - EasyAppIcon helps you to create your own app icons easily. Supporting Android Adaptive Icon!
Flat Icon Generator - Create stylish, flat icons for Android apps.
Ayecon - Ayecon is an app that allows you to easily make icons according to the required dimensions.
App Icon Maker - Create icons for mobile app stores online for free.