Just stare at everyone and don't say a word even when you're spoken to.

get pissed and trash the office. then be all lovey and apologetic.

i would do that. totally.
who cares if there's space? knock all the dustbins and shit over with your skates.

have sex on your desk.

Kiss everyone, even those you don't care about or know while you have saliva dripping from your mouth.

Accidentally I have just pointed the telephone handset towards the office fan and held it for a few seconds because a person was being rude.

Sadly no room to rollerskate but I could open a packet of prawns and leave them somewhere nice and warm. Only thing with that is I wont get to see the results.

Yes any type of shellfish is pretty wrong, infact most types of fish are pretty gross.

Ok so I plan to drink a few guinnes's at lunch then let nature take its course.

Right I don't know if this is possible but set up a three way phone call with someone without them knowing, with the third phone being another one in the same office an which is near to the main one you're using. Then when the person you are talking is talking stick the two phones together, earpiece to mouthpiece, and I think you should get some feedback.