Pretty much anything you wish to buy.
thats the point, people just don't know what they want and/or don't know how to find deep web for example, i'm sure you can buy lots of crazy stuff there, not even talking about drugs, not crazy enough for you, human organs might be there too
There are not that many things that you can buy with Bitcoin and that is really bad. I hope that it will be more acceptable in the future.
And that more people will know about Bitcoin so they will also going to use it. That will be so nice. But you never know what will happen...