Well, so far I may have 'accidentally' done these:
Drop an alternator on his foot (Actually, that was an accident, he bloody stinks and he was being a nosey bugger trying to see what I was doing so was right next to me... Hence why I dropped it as there was a sudden "HOLY FUCK WHAT IS THAT SMELL!?" thought."
Spilled brake cleaner on his bag...
Moved half of his bolts for a starter motor he was taking apart (and had already broken) to various places in the workshop, and leave a note explaining where they are... Badly. Ie: Keep walking left to find one. (Did this on my lunch break)
And, buy food for people when I tell him I have no money...
Yeah, we really don't like him.