ORIGINAL: dcairns
Watch out for cashiers checks in general. They are easy to fake. You need to wait for it to clear the bank before turning over the goods. Otherwise, you just gave away what you were selling.
With most of them, that isn't even the worst of it... they couldn't care less about the item you're selling.
They just hope you'll be naive enough to send them a check for the balance remaining.
If they get your stuff too... that's just a bonus. (Though they typically won't even try to receive it)