Apple Watch UI Kit - Quickly create Apple Watch app prototypes
Mockuuups Studio - Fast and easy way to create product mockups on macOS, Windows and Linux.
MockMagic - A free, easy-to-use device mockup generator
Placeit - Generate realistic product shots in seconds
Module 02: Layouts - Professional toolkit for UI/UX design
Mediamodifier - Create beautiful designs and product mockups in seconds.