The most un-ethical thing I have done was to take one of the OLPC XO laptops and convert it into a MITM machine, rebroadcasting the SSID it connects to while routing and logging all traffic anyone who connects to it generates. It took a weekend to setup using pre-existing tools and scripts and can be deployed anywhere I want within 2 minutes and run for up to 6 hours hidden in the bottom of my backpack. It was a fun experiment, and surely made me more aware of just how vulnerable I was outside of my home network.
Another point of interest, this weekend I hacked on a Minecraft bot for the Alpha version. In order to understand and dissect the connection protocol I needed to recreate, I used wireshark to dump and parse how the client authenticates and connects to the server. Even that transmits your username and password in plaintext.