MadView3D is a 3D model file viewer. It's a standalone application made with GeeXLab and coded in Lua.
MilkShape 3D is a low-polygon modeler, which was initially designed for Half-Life. By and by many file formats and features have been added.
Half-Life Model Viewer 2.0 is a brand new tool based on HLMV 1.25 and Jed's Model Viewer 1.36 that provides an entirely rebuilt model viewer.
The Blender Source Tools allow Blender to import and export Studiomdl (.SMD) Data and DMX model files.
This is the MDL Decompiler used to decompile all half life 1 (goldsource) models, use this program along with half life model viewer.
Fimg is an image editor for sprites and similar assets in Quake by FrikaC for Windows.