A short demonstration video of scripted, breakable glass in Call of Duty 2 (v1.3)
Breaks even from throwing a nade through it!
Glass can stop bullets or let them pass (shoot-through in this video).
No impact marks shown due to Quake 3 / CoD2 Engine Limitations (script_brushmodels can't have decals on surface, would be too much processing moving all with... thx 2 IW)