Okay, I have to get something off my chest. Don't worry, it's not the end of the world but I need to address something... yes, I hear what you are saying about my propensity for the word "giggle." Hell, I even agree to a degree.
I have a glossary of terms to describe laughter that I got back in high school for a creative writing class I took way back when... you know after avoiding the rampaging dinosaurs.
Smirk: Slight, often fleeting upturning of the corners of the mouth, completely voluntary and controllable.
Smile: Silent, voluntary, and controllable, more perceptible than a smirk; begins to release endorphins.
Grin: Silent, controllable, but uses more facial muscles.
Snicker: First emergence of sound with facial muscles, but still controllable
Giggle: Has a 50 percent chance of reversal to avoid a full laugh; the sound of giggling is amusing; efforts to suppress it tend to increase its strength
Chuckle: involves chest muscles with deeper pitch
Chortle: originates even deeper in the chest and involves muscles of torso; usually provokes laughter in others
Laugh: Involves facial and thoracic muscles as well as abdomen and extremities; the sound of barking or snorting
Cackle: First involuntary stage; pitch is higher and the body begins to rock, the spine extends and flexes, with an upturning of head
Guffaw: Full body response; feet stomp, arms wave, thighs slapped, torso rocks, the sound is deep and loud; may result in free-flowing of tears, increased heart rate, and breathlessness; strongest solitary laughter experience
Howl: Volume and pitch rise higher and higher and the body becomes more animated
Shriek: Greater intensity than howl; a sense of helplessness and vulnerability
Roar: Lose individuality; i.e., the audience roars!
I have used this glossary of terms to describe laughing in my writing and while I agree I use 'giggle' too often, it is the term that perfectly describes what my mind sees when I'm writing the scene. I will endeavor to use these descriptions more fluently in the future and try to stay away from 'giggle.' Unless 'giggle' is just too damn perfect of a description of what is going on during the scene!
Tee Hee!
--Shinerdrinker