We all know Adobe CC and Cinema but here are some lesser known but useful pieces of software.
Mischief Paint - Love this software. It behaves like a raster based paint software but has infinite resolution like vector based software.
XNview - Nice image browsing software that supports 500 different formats
Krita Paint - An increasingly interesting paint program.
Sculptris - Super simple 3D sculpting software
Wings 3D - A very simple modeling program. A nice program to learn some modeling fundamentals if you don't want to spend any money and Blenders UI is too crazy.