The only woman to ever make it big on a coin is Queen Elizabeth. In America, women just don't circulate. Take the Walking Liberty coin that Roosevelt commissioned, or the Susan B Anthony dollar coin that no one has ever heard of.
The newest addition to the ladies of coinage was the Sacajawea dollar, first minted in 2000. The unpopular Susie coin looks confusingly similar to a quarter at first glance. To combat this, the Sacajawea dollar is a dull gold in colour (that actually will rub off with time), and again only a little heavier and larger than a quarter. Great combat force.
Today the boy behind the grocery counter almost wouldn't accept A Sacajawea dollar, he'd never seen or heard of it before. And then he couldn't find a place for it in the drawer. Tomorrow shall I try to spend my two dollar bill?
But really, there aren't that many obscure monies. There is an anonymous fellow who drops some very old gold $20 coins (worth 800 bucks apiece) in a Salvation Army bucket in the northeast every Christmas. But other than that, except for the two dollar bill they're all in recognisable increments- nickles, dollars, half coins (sung about in the Bazooka Bubble Gum song), and people don't find the "new" state quarters confusing. They look as much like a quarter as a wheat penny looks like a Lincoln head penny.
I apologise to those from foreign lands who may not be familiar with the history and changing face of American currancy. I must say, though, that the most reassuring coins I have ever seen are British. They feel like money when you've got them: they're thick and heavy and feel like they have worth.
Compare this to Japan's plastic coins, which honestly do feel like Monopoly money, or the old Austrian schilling, where seven equaled an American dollar, and it's easy to see why England is sticking with the pound. That's incredible economic security, a coin that feels valuable and important in your pocket.