In Seattle we've banned the cheap plastic bags that blow around and get stuck in trees. There are many, many fewer tree-stuck-plastic-bag-ghosts to be seen around now. We've also put a mandatory 5c fee (not a tax, sadly) on paper bags; there are many, many more people bringing reusable bags to the supermarket.
(Ignores, of course, whether these reusable bags are better for the environment holistically -- having lots of yuppies buying synthetic shopping bags made in China and shipped to Amazon DCs, then having them individually shipped out in Prime boxes, etc. before being used is probably worse than just having pulp grown in America made into bags trucked en masse to the grocery and generally recycled or composted.)
Regarding carbon credits -- soon that will be not only feasible but tokenized and sub-divisible. See http://sparkchange.io/
You must live in the alternate universe where everyone litters.
No, some people just don't litter. Whole cities where people don't litter! Sometimes, there is a clear protagonist and antagonist.
As an aside: an* effective means of keeping that cup out of the ocean is also to buy all the cups and not use them. Pretty much the exact OPPOSITE of a "pigouvian tax." Isn't that crazy?
What if we bought all the oil and didn't burn it? What if we buy all the land it's under? Or more realistically, what if I bought carbon credits in cap and trade and didn't use them?
Greg Mankiw has doomed a generation to inside-the-box policy with his inane textbook.