There's this new slot:
What does it do? I've spent some cents only to receive cryptic phrases. The best use I've found for them is blowing them up.
After playing around with the slot in the image, and with the help of the wiki, I've found that, in addition to the cryptic sentences, there are also a lot of useful rewards including:
Here you can see my results after playing for a while (I failed to make it blow up by itself, so I used a bomb):
It can become a little cluttered, as you can see. I also had 3 more soul hearts and 1 heart container, but I wanted to kill the boss before finishing my experiments.