I accidentally deleted the Facebook chat history I had with someone. Wanting it back, I quickly whipped up a program for my Teensy to download and executes a Java app I wrote. The Java app gets the Facebook cookies, decrypts and uses them to read the chat history which will then be sent to me. Now all I have to do is insert my Teensy via USB and I'll have my chat back! *mission impossible music playing*

USB ports are such a vulnerability.
Using a device as cheap as a Teensy you can easily execute whatever malicious software you'd like on a person's computer.

I love spending my night not being productive because I spent the whole night looking for a bug. A bug that ended up being an eensy-teensy missing letter