- Sell them
- Make fraudulent purchases on them
- Create real-world cards out of them
To create real-world cards, you need blank cards to start with. These are known in the underground as "
blank plastic".
And there are online stores for blank plastic. Here are some pictures from one:

Above: Collection of "blank" Visa and Master Card cards.

Above: Gold embossing demo. Still missing the hologram sticker.

Above: Finished product.
Notice the card holder's nameā¦P.S. Also see our post about
credit card holograms.