I suppose it's hard to elicit good third party software tools for game dev if I don't have a stated requirement. I'll have to think about it some more and do research when the time comes. Arg, thinking about it though, it seems I know what to do so I should just start building the game itself. I suspect I'm falling into a bit of an analysis paralysis trap.
So... tomorrow I will get some solid work done!!! Coffee, music, and work!
Yes, I understand. It is easy to get bogged in research and design while dead in the water with actual game creation results. The third party software must be chosen based on your needs because there are so many of them out there. Also, the personal preferences of users are really opinion, so you need to try them for yourself to know what will suit you.
There are many 2D (textures, sprites, and so forth) and 3D assets at no or little cost. I would agree with Ashaman to get some simple ones, even if they are low polygon and increase or customize the details for your needs.
Once you get the 2D skills with a program like GIMP and others, such as layering, then you will find the artistic cans opening for you. You really need a 2D foundation in order to make the game look good. It impacts even the quality of the 3D work in a major way and stand alone 2D work as well.