One thing that still seems a bit weird to me is the 1 Yen coin. It is small and made of aluminium, and seems to rapidly accumulate. Coming from a country that has discarded values below 5c, having a coin worth less than AUD$0.01 is very different.
The other important coin we have learned is the 100¥. Many machines will only take this coin, requiring changing other values to it to use them. In our hotel the washing machine only takes 100¥ and at the train station the lockers only take 100¥. From now on we will be trying to accumulate them rather than use them in transactions where another coin or note would do.