General:
* Roar
* Chortle
* Guffaw
* Howl
* Cackle
* Snort
* Bellow
* Whoop
* Yell
* Shriek
* Thunder
More specific:
* Giggle (for a high-pitched, lighthearted laugh)
* Chuckle (for a soft, low, and amused laugh)
* Squeal (for a high-pitched, excited laugh)
* Wheeze (for a strained, breathy laugh)
* Splutter (for a surprised or confused laugh)
The best verb to use depends on the context and the specific kind of loud laughter you want to convey.