I like really petty ones. The wee circles of paper from a hole punch are very versatile. I got a letter from Saudi Arabia, opened it up, boom, paper everywhere- that one’d taken some planning. Person in question left the organisation and when we sent out her P60, she ended up with paper snow in her breakfast.
Googly eyes have unlimited uses. Another colleague has had everything she owns googlied yet still didn’t notice, til going through US customs, that this included her passport. Apparently that gets treated pretty much the same as declaring yourself to be a terrorist.
I can read and use a mouse upside down for some reason so when I get my screen flipped I just carry on, that annoys the flipper more than it could have ever annoyed me.