The short answer is; anything you can get for less than its actual worth.

One way of finding cheap goods to resell is by finding misspelt items listed by other eBayers. Suggesting this tends to get you shot down in flames by non-believers - but it does work.

For example:

Consider one of the most popular video games of the last couple of years - Grand Theft Auto San Andreas.

If, in the middle of 2005, you could've bought this game for