On my 'bucket list' is an 1892 10 Gulden from The Netherlands. It's released for circulation and has a mintage of 61 pieces. The next year of mintage (1895) had many more, namely 149 pieces for circulation. Also, the 20 gulden of 1853 is quite a rarity with just 136 pieces minted. And released into circulation, of course.
In Norway, the first three 10 Kroner pieces are quite special, with mintage well below 25.000 per year (and no more than 2 years of mintage per coin). Otherwise, the 2 Kroner pieces minted under Oscar II have many years with a mintage well below 100.000 per year (three years with 25.000 pieces, for example), and the commemorative 2 kroner pieces of 1906 (100.000 pieces, I got one), 1907 (50.000 pieces) and 1907 with guns (27.500 pieces) are also quite rare for being circulation coins.
I think some of the rarest circulation coins that I currently possess are the 1972 2 Mils of Malta (30.000 pieces) and I have several of them. Also, I have a 1965 1 lira from the Vatican. Mintage 60.000 pieces and released into circulation. I might have more but I have to look it up.