Coins versus Bars
Gold coins are often more convenient than bars, and can often be bought for lower premiums than bars, weight for weight. When you need money, its also cheaper to sell some coins instead of having to liquidate a whole bar.
It is sensible to consider modern one ounce gold bullion coins as being one ounce circular bullion bars, guaranteed by a government rather than a refiner.
There is a large selection available, and the top gold bullion coins in the world are:
The American Gold Eagle
The South African Krugerrand
The Britannia (mainly because of tax benefits)