Q. said
The Royal Canadian Mint catalogue has some nice offerings. Take a look (they also have an online catalogue, www.mint.ca) at the 10,000 gram gold coin, with a denomination of $100,000. Price depends on gold price when you order plus a hefty add-on cost. The gold purity is 99.999.
In 2007, they produced a $1,000,000 gold coin of 100kg weight for the multi-millionaire collector."

Perth (Australia) Mint unveils world's biggest gold coin Weighing in at just over one tonne, the 99.99 per cent pure gold coin has been valued at more than $50 million.

A team of a dozen people have worked since late last year to create the coin which measures 80 centimetres wide and 12 centimetres deep, (read on)

Perth Mint website