Ask any serious wine investor and he will say that if given a choice, he will rather buy magnum sized bottles rather than the standard 750ml ones. Current wine-lore has it that the bigger sized bottles age better and brings a better price when sold in the future.
In Singapore one easily sees the magnum (1.5 litres) and occasionally the double magnum (3 litres which goes by the name of Jeroboam). Recently I got the opportunity to see two 15 litres sized bottles at AA French Wine's retail outlet. A 15 litres bottle holds the equivalent of 20 standard bottles of wine. Its called a Nebuchadnezzar (named after a Babylonian king). Both bottles were from France, each retailing for slightly less than $2,000.
If you are organizing a big dinner session at home, the Nebuchadnezzar will easily accommodate quite a few guests!