Blender
There’s all kinds of 3-D stuff these days: Movies, Games, 3-D Printing, etc. Blender is the tool for creating things that are 3-D. It works similarly to a vector graphics tool like inkscape, but keeps those vectors in a 3-D space. It has lots of different view points (think camera angles) to make the design of 3-D things doable on a 2-D screen.
I’ve used it to make models of my house that I then 3-D printed (at our local library!), now I keep a copy of my house in my house…just in case I forget!
Professionals have used Blender for all kinds of amazing things. Every year, the group that maintains it makes a movie using it (it also has a video editor built in). Lots of video game designers also use it to build up characters, tools, and scenery.
FLOSSing for lent 30/40