I didn't get to play mechanical puzzles until I owned a 3D printer.
I didn't know LiveCube until I 3D-printed a lot of puzzles and have a very good time.
When I finally heard of LiveCube - a building system for polycubes, which was designed for puzzlers before 3D printing era, and still considered desirable and handy for myself, unfortunately its website is gone, not much information is left.
After some deep digging, and remodeling with 3D printability in mind, here comes AliveCube:
Two 2-stud cubes connect to each other to form a 1x2; subsequently add cubes to reach target shape.
I deliberately give it a very tight fit. If tolerance's not right for you, adjust is easy, just fire up OpenSCAD and slide $stud_scale in the Customizer panel. It's a multiplier on stud's diameter. Even better, you can easily testprint different $stud_scale by just scaling teststud.stl in slicer.
The author marked this model as their own original creation.