Take apart an optical mouse

Step 6 More difficult to get at: Chips and SMT Components?

That leaves the more difficult components to remove. SMT components and things with lots of pins. You can stop at this point, unless there's something you really want.

There are some interesting chips, but they're PROBABLY not useful as chips for the hobbyist. The optical sensor is rumored to be usable as a low resolution camera (32x32 pixels?), but in the newer version of the mouse, the camera and microprocessor are put together on the same "mouse on a chip", so perhaps the camera is no longer accessible. The USB microcontroller on the older mouse looks to be a somewhat standard Cypress part, but is probably not reprogrammable.

The clear-packaged "Mouse on a Chip" is rather pretty as chips go. It might make interesting jewelery. I managed to get it off the board by heating the whole thing over a gas flame on the
reverse side of the board till the whole thing was smoldering and the solder was melted, and then THWACKing on a moderately hard surface. The house smelled bad for a week, in spite the exhaust fan; this sort of thing should probably be done outside if you're going to do it.