Gear is a simple way to generate involute gear This utility is designed 

Rhino Beam Tools is a rhino plugin built as a bridge between Rhino and specialized beam calculation software. ("Steel" , Bureau Veritas)

Dynamic 3D Sectioning and 2D Layouts for Rhino Helps create sections that update with model changes.  Sections can create outline curves,

A simple tool for quick output of tangent lines of packing boxes, with rich options and interfaces, automatically generates expansion drawings.

GH Python Remote is a special component that lets you use regular Python code directly in the GHPython component, like importing Numpy and Scipy.

Lutralutra is .ghuser files for Grasshopper and Math Functional Surface Generator.

Kitsune is a tool for creating parametric truss-grid domes, vaults and revolutionary surfaces, using coordinate-system transformations.

Discrete Design and Modular Aggregations with Grasshopper. Offers tools to quickly generate large aggregation of repetitive parts.