Fix remote controller button contacts
Use a pencil.

If the buttons are one of those silicone membranes with little black rubber disks on the back that are responsible for actually making the button-contact, the black rubber disks are just graphite-loaded rubber/silicone.

Taking a (preferably soft-leaded) pencil and rubbing it on the contact surface of the disks to get a nice fresh coating of graphite will typically bring it back to life for a while.

Alternatively, if you're after a longer-lived solution, a conductive-ink pen would probably also work nicely.