copper slug

Mr C- You are right and wrong. The cost of copper is pretty high, compared to most other metals(scrap is fluctuating between $2 & $3 a pound, lately). Thus, grounding/earth rods are available in solid and plated versions: (http://www.krispettlonlightningprotection.com/catalog/grounding.php)

If all you intend to do, is eliminate a fuse: solder a large gauge piece of wire across the fuse holder's terminals. Replacing a fuse, with a piece of copper, just provides two more contact points, for corrosion to form.