As the title says.
Never really dabbled in 3d stuff outside of some very basic drag and drop stuff years ago, so I'm just curious as to what the community thinks is the 'simplest' program to create 3D stuff for use in a Firefly enabled 3d fusion game. I'm not looking for AAA quality stuff - I'm happy with low poly prefab parts that I can just smash together if at all possible, but I'll take what I can get!
I should also mention that I am willing to pay zero dollars. That may complicate matters.