[testplzignore]

If you have a pair of scissors or are willing to ask people to take a brief bit of pain...

Hair.

Cut (or pull) off a chunk of hair from everyone in the room. Put in a big pile. You'll have hundreds of thousands of hairs. It will be a glorious mess :)

Now ask people in the room to grab a handful of the hairs and count them. Take the last digit of the each count - there's your random number. You could maybe get multiple digits from a single handful - just be aware of Benford's law.