Back in 2012 the camera down near Canadarm2's base went on the fritz, so a couple of astronauts removed them during a spacewalk. More recently however, the super critical camera attached at its elbow joint has started to get a bit fuzzy, so the Canadian Space Agency team figured they could use the arm to fix both problems at once.
First Dextre detached the fuzzy camera from the elbow joint, and reattached it down by the arm's base where the old broken camera was removed a couple of years ago. Then Canadarm2 went over to the Kibo airlock where a shiny new camera was waiting, and installed it at its own elbow in place of the old fuzzy one.
These cameras are pretty hefty at around 47 pounds each, and they are about the size of an old-school CRT-style computer monitor. They don't just snap into place like LEGO pieces, so for each operation Dextre had to unscrew a bolt and make sure it didn't slip between its mechanical fingers and fly off into the emptiness of space. That's a tricky task for a robot that hasn't been setup to perform the same exact job repeatedly.
Having this ability for the robots of the ISS to repair themselves could really come in handy as the ISS gets older, especially if the Russians stop giving rides to our astronauts as some sort of political retribution.