Thunkable - Powerful but easy to use, drag-and-drop mobile app builder.
Kite Compositor - A powerful animation and prototyping application for Mac & iOS.
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.
Adobe XD - Adobe XD is an all-in-one UX/UI solution for designing websites, mobile apps and more.
Bubble.io - Building tech is slow and expensive. Bubble is the most powerful no-code platform for creating digital products.
Marvel - Turn sketches, mockups and designs into web, iPhone, iOS, Android and Apple Watch app prototypes.