Today I replaced the button cell (A013 / LR44) batteries in some of my laser pointers.  Most of the batteries were dead and leaking, so now there is a contact way down inside the laser pointer barrel that’s now corroded, but is very difficult to reach.

Here’s an idea:

Instead of loading the batteries in the pointer with the negative contact (cathode) in where the leaks originate, reverse the laser polarity so the batteries can be loaded with the positive terminal in.  Now the inevitable leaking will still damage the contact, but it will be on the part you can get to and clean easily.