Some windows contain visible glass but do not react when shot. Make these window panes break when hit by bullets, with appropriate shattering effects and sounds. This would improve environmental interaction and make combat feel more responsive and realistic.
that and also like another person suggested with being able to shoot out lights, I would also add destroying TV's or computers ect
I agree, it shouldn't just affect glass. Destructable items throughout the maps would definitely add to player immersion while in a gunfight, stray bullets hitting glass, windows, light sources, random items on tables and countertops, etc. Not only does it add to the immersion, but it also would allow light sources to tactically be destroyed to darken areas. Also, its just cool as hell to see the aftermath of gunfights throughout the map as games progress.
Shooting lights out would be good with night vision