Gold Bar

Gold Bars are first seen in Luigi's Mansion. They account for 100,000G each and are often found in treasure chests.

Bars also are used for storing money in Paper Mario: The Thousand-Year Door and Super Paper Mario. Mario cannot use them in combat in any way, and he can only sell them for coins. If Mario buys a 100 items at a store, he'll get a Gold Bar for free. If he buys 250 items, he'll get a Gold Bar x3. Single Gold Bars are worth 100 coins each, whereas Gold Bars x3 are worth 300 coins apiece. Oddly enough, Mario can give a Gold Bar to Saffron to turn it into a Golden Meal, a worthless item worth only 5 coins.

Wario has a lot of Gold Bars as seen in Wario World. The cover of the game has Wario in a pile of money, and in that pile is a few gold bars. Inside the instruction manual of the game in "From Richers to Rags" of a bunch of Gold Bars can be seen.