Ditto about Elite, although once I found how easy it was to edit the save file to change money and kill count I kind of fell out with it. All trust was gone

. I remember getting the tape version on the BBC B, then finding out the disc version had lots of stuff that wasn't in the tape version, so pestered my parents for a disc drive (at something redic like £200 for 100kB). Finally got one though!
X-Wing was my downfall at uni. Would have been my 2nd year 92/93, probably dropped a grade from redic late night sessions repeatedly trying to destroy the Star Destroyer instead of revising. That and 2 player Mortal Kombat (FINISH HIM!).
Sam & Max though. Genius. Day of the Tentacle too. Similar twisted humour.