I'll own up to it

I shattered a dewar for a 500 mL round-bottomed flask today. I was wearing gloves and goggles, the dewar was in my hood at arm's length, and no one was hurt, but the BANG! was so loud that I was trembling for the next five minutes.
Here's a link to Princeton's lab safety website and its recommendations on dewars.
A dewar is an insulated container that I use for my cold baths in the lab. The most common cold bath I use is a mixture of dry ice and acetone, which has a temperature of 78 degrees below zero (Celsius). It's important to run some reactions in the cold to prevent uncontrolled reactivity.
Anyway, this particular dewar is made of glass that is lined with silver. The whole thing is surrounded by aluminum metal. The reason a dewar insulates so well is that it's a double layer flask with a space for a vacuum between the walls.
Dewars implode when they are broken, meaning that they collapse in on themselves instead of exploding outward. However, there's still a risk of small glass particles flying around and injuring someone.
The most famous dewar out there is the humble Thermos that you took to lunch every day in grade school.
In homage to the Tenderbutton style of blogging, I've posted pictures of the dewar so you can see the damage for yourself. I think I needed a better camera for this. The aluminum/ glass reflects light really well and is hard to photograph.
Here's a regular dewar.

Here's my shattered one.

Kids, don't try this at home. We're trained professionals.