Subtle:
* Tink
* Click
* Snap
* Crackle
* Shatter (can be subtle depending on the intensity)
More Dramatic:
* Crash
* Smash
* Splinter
* Clang
* Shatter (loud, dramatic version)
* Thud (if the glass falls after breaking)
Descriptive:
* Screech (if the glass breaks with a sharp, high-pitched sound)
* Shiver (if the glass cracks but doesn't break completely)
* Whimper (for a delicate, fragile break)
The best word to use will depend on the context and the specific type of glass being broken.