During my last post I talked about Paint3D and its uses for 3D games. There were some pros and cons, and it depended on what you wanted out of it. The biggest pro that it seemed to have going for it was the large library of models to access.
Today I will talk about 2 other options out there. You have Sculptris and Blender, and each free to use. Sculptris doesn't have near the capabilities as Blender does, but that doesn't mean you should count it out. They could be pair together to create some interesting characters.
Let's start with Sculptris. This tool is from Pixologic, the same creator for ZBrush. ZBrush is an incredibly powerful tool that is looked at as the leading software when it comes to 3D sculpting. Sculptris has a lot of the same functions as ZBrush, but scaled back quite a bit with overall function.
I currently have Sculptris on my computer and actually enjoy using it. I do plan to upgrade eventually, but it allows me to accomplish what I want. You can sculpt the 3D clay, apply or remove symmetry, and adjust overall triangle counts up or down. It even has the ability to apply 3D paint and texturing to your model and add in some normal mapping for additional surface texture. Once done, you can export it out and combine it all together in the game engine.
Another option is Blender, and to be honest has a lot going for it. Not only can you sculpt and edit geometry in it, but also comes with its very own game engine built right in. You can create all of your geometry, rig and animate it, and create a game all within the same software.
Now, I have messed with Blender once years ago and it was a bit hard for me to understand the interface and by what I have read online some people have said the same thing. Granted, just about every software will have some people that have issues learning it and others that catch on quickly. Regardless, I would go to their website and read about what it has and watch some videos on it.
That last part is one of the biggest things to help you decide on what you want. Read up on it, whether that be all of the features, reviews, and content that was created from it. Heading to YouTube and searching on both Sculptris and Blender will help you see what they are each capable of.