Cash
crypto currency
amazon giftcard?
physical goods
greendot?
western union?
Lets add to the list....
greendot moneypaks are reversable, but payment from a greendot debit card is not.
cash can be faked
amazon giftcards can be chargedbacked(very unlikely you being able to do so successfully)
privatemoney
web money
international wire transfers
sex
your virginity
payments made to bfl.