Inkscape is professional quality vector graphics software which runs on Windows, Mac OS X and GNU/Linux. It is used by design professionals and hobbyists worldwide, for creating a wide variety of graphics such as illustrations, icons, logos, diagrams, maps and web graphics. Inkscape uses the W3C open standard SVG (Scalable Vector Graphics) as its native format, and is free and open-source software.
Krita is a powerful vector graphics creator with aheavy focus of digital painting and illustration. It is mainly used to design comic books. It is free software with advanced templates and features.
Blender is a 3D drawing creation software. Topmost famous animators use Blender to make short films, feature films, and Tv shows, etc.
Its interface is quite complex at first, but when you go forward to design, then it is easy. It has a lot of customizable features and , you can also create your extensions and features that the way you want to design.
It helps you to handle the photorealistic rendering, sculpting(different type of brushes), game creation, and fast rigging.
Skencil is a vector drawing application. It is available in Linux/Unix/GNU-like operating systems. It enables us to create some great diagrams and illustrations and useful drawings. Skencil is built with interpreted language, i.e. python, and it is very high-level object-oriented.