Similar in meaning:
* Giggle
* Snicker
* Grin
* Titter
* Smirking
* Chuckle
* Laughette (French)
Slightly different in meaning:
* Laugh: More robust and full-bodied
* Guffaw: A loud, boisterous laugh
* Roar: A very loud, deep laugh
* Cackle: A harsh, shrill laugh, often associated with amusement or malice
* Snort: A sudden, forceful expulsion of air through the nose, often accompanied by laughter.
* Wheeze: A short, strained laugh
More subtle:
* Smile: A gentle expression of amusement or pleasure
* Beam: A wide, radiant smile
* Grin: A wide, toothy smile
The best synonym for "chuckle" will depend on the specific context and the tone you want to create.