For value, history, and not a big premium over melt I would add in early 20th century American gold coins. As Paint Your Wagon suggests, you want something that is familiar, easy to authenticate and with known dimensions specifics etc. Last night on a discussion forum on their BST board I bought a 1910-S $10 gold piece for $460. Melt on that coin right now is $438, a markup of $22 or 5%, which is less than half ounce AGE's are selling for presently. You have to look for the bargains, but they are out there. Over the last weekend I found a Hungarian 100 Koronas weighing 0.98 ounce of gold for something like $850 on eBay, right now as of this morning that coin will melt for $895. It is a large and beautiful coin like this:

These were a bit more popular when they were restruck by the Austrian mint in the 1980's than they are now because don't quite have a full ounce of gold in them.
I just wish I could find gold coins in appreciable quantities like I could before, rolls of AGE's etc. For the now those days are history.