Welcome me here to help get some idea about useful softwares.
I use Unity 5 with Blender. They are both free and very useful.
When I create textures or tweak them, I use Gimpshop, a free Photoshop alternative.
When I want to record sound for my cg film or game, I use Audacity, a free audio editor.
And lastly, when I compose a soundtrack for my games or cg films, I use Mixcraft. It is not free but it’s well worth the money!