You can sell everything that has made you happy in the past or that you don't need in the future. Whether it's an old dresser, concert tickets that you cannot use yourself, a lovingly restored bike, your old favorite blouse, your used car, rare sunglasses or your PlayStation game that is waiting for a new high score. Shpock is the marketplace for everything desirable.
Illegal items are prohibited even at Shpock. Generally, it is not allowed to sell living creatures or food. Moreover, you are not allowed to sell things, that might physically or emotionally damage someone, or are regulated by law, i.e. that are not allowed to be sold to people without a certain license. This is also true for fake/counterfeit products and pointing out that the item is fake does not make it any more legal.
In the following, you can find a small overview of forbidden items: