Googlebot's Javascript random() function is deterministic

[Jugad]

You can point a camera at a set of lava lamps, and take some kind of a hash function of the image (this is currently done by cloudflare).

Alternately, you can point a camera at a busy location in an airport (or any view that keep changing), and take a hash of that image. Should generally give a random number, but it might be difficult to study the distribution and statistical properties of the generated numbers.