Some old 3dsMax Tools I have scripted in the past :
- Curve Key Editor
- Skinning Tools
- Rigging Tools
- Biped Interpolation


Maxscript scripting

In order :

° Curve Key Editor :
A MotionBuilder-Like Tool that add a button on the right of a curve editor window to edit Keyframe values :

- Edit multiple keys time and/or value using add/substract/multiply/divide operator
- Edit In and Out Tangents
- Set the Out of Range Type

° Skinning Tools :
A ToolBox to help skin :

- SkinWrap a mesh to another one and collapse the modifier into a skin modifier or not
- Switch skin weights between 2 bones, or send all weights from 1 bone to another. This can be also done only by using a selection of vertices
- Shortcuts to very useful Skinning parameters : Bones Affect Limit, Remove Zero Weights…
- Remove from a skin modifier all bones that don’t have any affectation
- Expose unnecessary skinned vertices

° Rigging Tools :
A ToolBox to help rig :

- Create your own list of shapes, and then create and name controllers from it. Make your own convention for them
- Transform them into smaller ones, or edit their size.
- Duplicate them for each side of the body
- Expose distance between 2 nodes
- Create Spring chains from any class of nodes, assign them a specific color and then edit their own effect or multiple ones at same time

° Biped Interpolation :
A Tool to simply edit Biped Keyframes :

- Set the interpolations of your Biped keyframes into Smooth, Linear or Stepped mode (on All Frames, the selected keyframes or the current frame)
- Shortcut to edit TCB parameters