I cannot believe anyone reading this has not heard of the "Nigerian Scam" (also called 419 after the Nigerian anti-fraud statute). The most common, that I receive every once in a while, has to do with someone -- a widow or son of the recently assassinated political leader someone-or-other in some African nation. (I suppose they assume, rightly, that Americans especially won't have a clue of this particular person exists, was recently assassinated, etc.) There are millions of dollars in a bank account and the sender of the email heard about your integrity doing an Internet search. They suggest a money laundering scheme for which the recipient gets %10 just for playing... er, helping."
I just read a fascinating piece on this at news.yahoo.com/s/latimests/20051020/ts_latimes/iwilleatyourdollars describing this in interesting detail.