Thunkable - Powerful but easy to use, drag-and-drop mobile app builder.
Retool - Build custom internal tools in minutes.
MIT App Inventor - App Inventor is a cloud-based tool, which means you can create apps for phones or tablets right in your web browser.
zeroqode - Build your app up to 10x faster with no-code app templates
Android Studio - Android development environment based on IntelliJ IDEA
Anvil.works - Build seriously powerful web apps with all the flexibility of Python. No web development experience required.