NEW Lite version is now available for free here

An automated script to texture Unity Terrains based on a wide range of configurable parameters.
Very easy to use, much less complicated than other tools with a user friendly interface and design

Includes customisable layers, with the option to use up to 12 textures for each, and several options for the distribution and blending of these textures.
Customisation options include, though are not limited to: sea level, snow altitude, cliff steepness & texture perlin configuring.

With this you can create virtually any terrain you want in just a couple of minutes - whether it's grassy, rocky mountains, dessert, volcanic, glacier etc.
Check out the screenshots and videos to see what this tool can do with ease.
A demo scene is also included with an already generated texture that you can adjust the settings for to see the effect

The texture can be generated from a button click in the editor and can also be previewed live as you update the settings

Documentation for more info
Note: this asset uses the old splatmap system which is now obsolete. The tool still works for me in Unity 2020 but you will get warning/error messages during use.

TerraTex - Automated Terrain Texturing/Splatmap