What's a simile/noun used to describe something shaking violently?

Synonyms for shake violently:

1. Churn - Stir about, cause to froth; agitate violently; turn or throw up violently.

"Waves churning in the storm."

2. Convulse - Shake violently; agitate or disturb severely.

"Tremors that convulsed the countryside."

The idiom shake like a leaf is well known, but it's also a cliche. I'd avoid it.

rock

To cause to shake violently
An earthquake rocked the town. m-w

The earthquake rocked the building; the building rocked Chambers

It was an area of active volcanoes, and when the earthquake rocked his wooden house, he initially thought that it must be a nearby eruption. ref.

This is clearly not another of this word's meanings, to cause to sway back and forth, as in rock the cradle.

You choice may depend on how violent the shaking is, any subtleties about the movement, and the size of the object: ...bucked/wobbled/rocked like an off-balance washing maching.

Here are a few examples, some perhaps more useful than others:

The room shook as hard as...

• an old-time Quaker revival
• an addict in withdrawal
• a Volkswagen bus filled with hippies
• a Chihuahua in winter

Please forgive me...my sense of humor is a bit twisted. But maybe one of these will jog your creativity.

Perhaps the idiom shake like a leaf is suitable.

shake like a leaf: (thefreedictionary.com)

To tremble violently with fear or nervousness.

You could say shake like hell, but note that it is informal:

Some people use like hell to emphasize how strong an action or quality is.

• I used to shake like hell. The Sun (2015) (Collins)

It does remind you of the idea of all hell broke loose.