Uggh. When I travel in Europe--especially Germany with its remaining heavy use of cash--I hate coinage that is sufficiently valuable that I can't just basically ignore it. The US seriously tried to do a dollar coin (the Susan B. Anthony)--which was arguably ill-conceived for at least a couple of reasons but I'm very happy with US coinage being basically loose change although I'd be happy to eliminate basically disposable pennies and maybe even nickels.
Though to tell the truth I normally use cash so seldom and/or at so few places in the US that it probably doesn't matter.
See https://en.wikipedia.org/wiki/Dollar_coin_(United_States)#Sa...
Funny, that's basically the inverse of the reason I liked it — it allowed me to ignore cash some time.
The wonders of search helped me find my old comment without scrolling, here's more detail: https://news.ycombinator.com/item?id=22502882