Pure Skill Minesweeper
I had a co-worker who played minesweeper all day long on his Linux workstation which I had remote access to.  I grabbed the source code for the exact version of gnome-mines he was using and compiled my own version with some back doors.  I would also launch an xvnc server so I could see him playing from my desk.  Sometimes I'd have people over at my desk watching him play.  It was hilarious.<p>I could enable various features while the game was playing.  Features included:
* Always lose on first click
* Always win on first click
* Force a guess in all 4 corners... so even if played perfectly he'd have to make 4 guesses.
* Load custom designs from text file.  For instance I had some that spelled things out.
* Every click would be completely surrounded by mines (i.e. the number 8) until half the mines were exhausted.  This one was fun because I remember him not believing it and actually clicking on a mine.
* Ridiculous sounds when he won or lost