http://mdgdxj5d7wlgq3m6e4fvca5sgnbvejsyjh3sqh3p3tfngcnrhpuy3aid.onion/2013/greetings.html
It is both a high-five and at the same time a slap, but you don't know which until felt. It's not really a paradox though. I mean if your greeting involved a finger, depending on how you showed it and/or which orifice you jammed it into or if any orifices are involved, we can usually determine whether the response to that greeting will be a high-five or a slap.