I don't have as much of those... :-(
I think these are about all of them:
-one time at work someone was making fun of me behind my back as I was working on his computer. I didn't say anything of it, but afterwards I got into his computer by \\<computername>\c$. he got a few games installed that...somehow ended up missing a few files from them.
-in another job there was this one guy whom I couldn't stand and who should have been fired on the spot for even half the stuff he did (but there he somehow ended up running a facility). For some strange reason, he not only had admin rights on his own pc (this wasn't a relaxed company like the one described earlier) but actually had WBFS manager on his system. I knew that if I confronted him with this he would complain about me behind my back, so I just removed one essential file from it (a .dll file, iirc). A couple months later, I did the very same thing.
And there was this one thing that may have been evil, but was something I had to do as administrator. You see, that second job also had a very weird labyrinth of folders and subfolders to which divisions or users had access to through some very obscure rights nobody even pretended to understand. Nonetheless, we as a company were charged on a monthly basis for the stuff that was on it. Not especially high, but enough to use spacesniffer to figure out which were the highest ones. And sure enough, somewhere in those folders was one that was so huge it took over half of the...perhaps thousand different folders. It was filled with ripped movies. Some made years before, some as recent as a few weeks before.
As this was a retarded company, there was no way I could file a complaint (it would've backfired into me not having properly maintained a structure I only inherited from someone who had to do file administration as a side job as well). And I really wouldn't want to piss off people I had to work with. So I put the whole folder in yet another subfolder, and put a note in the folder itself saying I understood why they wanted to do it, that I wasn't the police, but whether they would please not use the network drive. I'm not sure whether I mentioned it anymore, but the price our company paid just for stocking (and probably daily backups as well) for that folder was well over that of a monthly DVD.
As I expected, nobody replied or wrote anything back. So a couple weeks later, I just removed the whole folder.