

XBreaker is a fantastic plug-in for fracturing geometry by Nitroman. It works with primitives, nurbs objects, splines and polygons. Integrating seamlessly with mograph and modynamics, it takes just a few quick clicks to set up an entire scene. Integrating seamlessly with mograph and modynamics, it takes just a few quick clicks to set up an entire scene. (Requires Cinema4D 11.5 and Mograph)
Download: XBreaker ver. 1.71 (Put the file in maxon/library/scripts)
Nitroman’s official website: Cinema4D Plugins
Pariah Studios: XBreaker updates
Version history: XBreaker forum thread
Tutorial videos: Nitroman’s YouTube

Here is a list of tutorials that give good breakdowns on how to make grass in Cinema 4D.
Grass Tutorial Cinema 4D by 3D Tutorials
Very quick and simple way to make grass.
Hair-Force 1by Base 80
One of the best tutorials focusing on animating grass.
How to create 3D grass by Adam Woodhouse
A quick and simple way of using the Fur object to create realistic grass.
Hair engine. Grassy scene by Rob Redman
An insightful video tutorial on how to make a grassy scene.
Cinema 4D Tutorial: Grass by Tom Decker
Another simple step by step tutorial using the Fur object.
Part 1 Part 2 Part 3 Modeling realistic grass in Cinema 4D by Matúš Laco
A complex approach to making realistic grass.