Past two weeks I toot ethical hacking course where we mainly worked with Kali linux VM. You can do many interesting things: generate exploit payloads, set up proxies, capture and modify packets, sniff wireless (add USB WiFi card to VM), crack WEP and dictionary attack WPA, crack password hashes, scan for vulnerabilities, get network statisttics, dissasemble Android apps.

It's Debian based. Coolest course I took this year.