Kodular - Much more than a modern app creator without coding
Anima App - Design, get feedback, convert to code, publish, iterate.
Thunkable - Powerful but easy to use, drag-and-drop mobile app builder.
Timeline for Sketch - Create beautiful timeline animations in Sketch
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.
Invision - Prototyping and collaboration for design teams