Hack-A-N900/Wall Of Bricks
Boot loop? hang? Congratulations, you made it! Please share how.

Tried to enforce bash as system default shell
How:
rm /bin/sh ln -s /bin/bash /bin/sh
Result: boot loop.
Tried to overwrite /lib from a running system
How:
cp -a /somewhere/lib/* /lib/
Result:

Tried to write a disk image to an extended partition
How:
# /dev/mmcblk0p4 is an extended partition dd if=image.dd of=/dev/mmcblk0p4
Result: corrupt partition table