General:
* Chuckle
* Giggle
* Grin
* Snicker
* Guffaw
* Chortle
* Titter
* Wheeze
More specific:
* Hysterical: Howl, roar
* Nervous: Cackle, giggle, snicker
* Sarcastic: Scoff, sneer
* Quiet: Smile, smirk
Figurative:
* Enjoy: Relish, savor
* Scoff: Disdain, mock
The best synonym will depend on the specific situation and the type of laughter you want to describe.