I know some of you go around bricking your OUYAs so hopefully this helps.
Some of you have other methods, feel free to share.

1) Plug a USB keyboard into your OUYA while it's powered off.
2) Power on your OUYA and let it boot as far as it can.
2.5) Find the sysreq key on your keyboard. On most extended keyboards, it is Print Screen.
3) Hold down Alt and Print Screen
4) Press and hold ALT and Print Screen (sysreq) Key.
5) Press i and hold for 5 seconds then release. Repeat this step for 30-45 seconds.
6) Press the HOME key
7) Select "wipe data/factory reset" and hit Enter key.
8) Select "Yes -- delete all user data" and hit Enter key.
9) Select "wipe cache partition" and hit Enter key.
10) Select "reboot system now" and hit Enter key.