The fastest service like paypal also seem to have the greatest risk, even cash is not completely safe because of counterfeits. What's the best way to mitigate trading risk to as low as possible? Some good suggestions I hear from this thread is：

tell buyer to send it as gift
avoid all services that have chargeback (though this severely limits the audience I feel)
go with the most reputable seller and hope for the best

it seems the best option is to tell the buyer to do a direct cash deposit. That way you see the payment right away and its irreversible to the best of my knowledge.