There's a big list here: https://t.co/OqoYN8MvMN
But it's stuff like:
- Evolved algorithm for landing aircraft exploited overflow errors in the physics simulator by creating large forces that were estimated to be zero, resulting in a perfect score
- A cooperative GAN architecture for converting images from one genre to another (eg horses<->zebras) has a loss function that rewards accurate reconstruction of images from its transformed version; CycleGAN turns out to partially solve the task by, in addition to the cross-domain analogies it learns, steganographically hiding autoencoder-style data about the original image invisibly inside the transformed image to assist the reconstruction of details.
- Simulated pancake making robot learned to throw the pancake as high in the air as possible in order to maximize time away from the ground
- Robot hand pretending to grasp an object by moving between the camera and the object
- Self-driving car rewarded for speed learns to spin in circles
All of which leads me to think that if you can't at some level explain how/what/why it's reaching a certain conclusion that it may be reaching a radically different end than you're anticipating.