If we haven't received them in our email inboxes, we have all heard of them. Nigerian scams attempt to try and con people into donating huge amounts of money in the hopes of getting a fair share of a multi-million dollar prize. Sometimes victims are lured to Nigeria (or some other country) and held for ransom or even murdered.
I responded in the summer of 2004 to such an email, always intent to leading the person along. Read my experience.