Several Small ones (ooh err)
not as involved as some of the posts (or as funny!), but from
my days working in Consumer support for a then large ITcompanya few spring to mind which might give some techs out there ideas:

The old swapping the M and Nkeys - Connecting another mouse or keyboard and making random movements or comments - Setting up an outlook rule when a collegue had foolishly left his terminal unlocked to launch our database again everytime a new email was received. -Taking a 'Print Screen' of the desktop hiding all the icons and then setting the new bmp as the wallpaper.

convincing one of our admin girls that left handed biros were available - (the ball point rotates the other way to make it easier for left handed people apparently)

Another favorite standby - Can you call back Mr C Lion? -
The last girl that did this said 'how rude they've put the phone down on me im going to call them back and give them a piece of my mind'

Covering an entire car in warehouse shrink wrap and on a seperate occasion filling one with those polystrene packing chips.

Convincing a none too bright tech that the game 'Black and White' which had just been released and that he had a copied verion of had sophisticated anti piracy software (which nicely tied into a then current news story about the game having some spyware in it for that purpose) and that the police would be raiding his area shortly - caused him to bury his hard drive in his back garden and but a retail version of the game. Cant remember if we ever told him the truth!

That was also the same guy that we setup a rule in his outlook that forwarded all his private emails from his girlfriends hotmail account to a public folder - cue much piss taking.

And finally - Setting up various autotexts in outlook when one of the girls left her machine unlocked subsituting 'monday' for 'tuesday' and "Love and Kisses" instead of 'regards' and various other things of that ilk - took about a month before she noticed! Idenied all knowledge.

To really spread mistrust throughout an organisation though just create your own organisation chart, remove all the existing heads of department, merge departments promote the most unlikely people to senior positions mark it something like "Quarter 4 reorganisation plan" and stick half way down the paper tray of a photocopier or printer - When its eventually spotted on the back of a printout and the rumors start, they'll be denied - Well they would say that wouldn't they if they're going to lay people off etc etc - Literally months of fun :-)

mutters something about length
(Titanix, Sun 16 Dec 2007, 18:36, Reply)