The point at which you have consumed so much alcohol, that you are incoherent, have difficulty remembering simple things i.e where you live, how old you are, how ugly you are, how ugly that girl your about to sleep with is. Being 'shit-faced' is usually an experience you only want to try once, and never again.
"Jesus christ!! did I sleep with that thing last night?? I musta been totaly shit-faced"
having reached the stage of consuming an undefinable amount of alcohol that the world according to yourself seems either:
a) pretty damn sexy b) very loud
c) uncontrolably unstable
d) all of the above
Most likely, once you have reached this stage, the enjoyment lasts only until you become in contact with someone that you saw/attempted to speak to that night.
John was so damn shit-faced that night he forgot the bad ass things he got into