I find duct tape and cable ties work very well. Bin liner bags and rope if you just can't stand to look at the person any more.
On a more creative note, spray glue, saw dust and an office fan have worked in the past.
Take the wheels off their swivel chair or connect their keyboard to the bosses monitor.
let the air out of 2 of their tyres and leave a portable compressor, one that doesn't work.
Finally buy a large cheap lemon meringue and cream pie and fake tripping ensuring you hit them right smack in the kisser.
If the above don't achieve the desired result drop me a mail, I have loads more,