Now known as A.D.H.O.C, MacHack was a conference for Macintosh programmers that began in 1986. Some 'hacks' that emerged from the MacHack sessions were implemented in later versions of MacOS. Recently renamed because of the negative connotations of 'hack' in the media.
Drank some Jolt Cola when I went to MacHack, stayed up all night and screwed up the stack...