GZDoomBuilder 1.06:

Fog rendering (including colored fog in maps in UDMF format).
Fixed lots of bugs in model loading and rendering.
Added "Toggle GZDoom Effects" button, which currently toggles dynamic lights, models and fog rendering.
Model loading process is more verbose now, so if something goes wrong, check Errors and Warnings window (F11) for details.
ColorPicker plugin:
You can now select surfaces in 3D-mode and then open Color Picker window to edit sector colors of sectors, to which these surfaces belong.
If nothing is selected, you can hilight a surface and then open Color Picker window to edit sector colors of sector, to which hilighted surface belongs.
If nothing is selected, you can hilight a Light Thing and then open Color Picker window to edit it's properties.