A paper clip bent into a "U" can be used to start an ATX PSU without connecting it to a motherboard (connect the green to a black on the motherboard header). One or more paper clips can make a loopback device for a RS232 interface (or indeed many interfaces). A paper clip could be installed in a Commodore 1541 disk-drive as a flexible head-stop. A paper clip can be used (unsafely) to temporarily bridge a blown fuse. The steel wire from a paperclip can be used in dentistry to form a dental post.
Paper clips can be bent into a crude but sometimes effective lock picking device.