DeP's M3 Model Editor
Uncreative names are the most descriptive. :)
This utility was designed for users who, for whatever reason, cannot use 3DS Max for making minor edits to models. It does not have very many capabilities, but because it is a standalone utility and not a plugin, it will preserve all model data that it is not programmed to modify. The original idea was just to hide unwanted parts of models and change the names of animations that exist in default SC2 models but are inaccessible to the editor (such as the Marauder's two-handed attack).
In its current iteration, this program only allows you to move one vertex at a time, scale the entire model (particularly for Terrain Objects), and modify animation names, material names, specular multiplier, and emissive multiplier. Before the middle of March 2012, it will most likely support editing material data, it may support modifying attach points, and the source code will definitely be uploaded.
I don't want to upload the code at this time because, in the event others actually want to work on it, I don't want separate versions to end up with a different feature list.