Best Circulation Find?

1927 Australian 3 pence.

Not only is it silver, it is old, and it is from the other side of the planet! So beats my IHC or V nickel just because how much traveling it did to come to me as if it were just a normal dime.

I received an uncirculated Cypriot 5 cent piece from the grocery store, a Monacan 2 Euro in change from McDonalds, and found that I had an 1898 Swiss half frank in my pocket when the parking meter refused to accept it.
Looking through ones change has gotten much more interesting in Europe since 2002!

Lowest mintage: one of these Armenian 50 dram commemoratives (don't recall which one offhand). Sure, they aren't particularly rare or valuable, but at 50,000 mintage that coin would beat anything else I could've found anyway.
Most valuable: slightly off-center Israeli 10 sheqel. It's a bit of a joke example - I hadn't found any other coins worth more than 10 sheqel (at that time, about $2.5; these days closer to $3).
Most unexpected non-foreign: Israeli 1986 "Edmond de Rothschild" 1/2 sheqel commemorative. (I think I should note that by "non-foreign" I mean that the coin was found in the respective country.)
Most unexpected foreign given by a cashier: Italian 20 lira 1973 (in Russia). Heard rumors of US golden dollars turning up in circulation, never actually got to see any.
Most unexpected foreign found when literally checking change (already given): Polish 50 groszy 1995... not many coins in that particular category.
Oldest: Soviet 20 kopek 1961. Not particularly interesting, and common enough that I think I've had two. Unfortunately, chances are that, unless I visit the US or Switzerland, my change will never have anything older.

I don't know what the "prettiest" coin was (Serbian and Armenian coinage is just generally pretty, but it probably doesn't count if I found it in Serbia and Armenia respectively, and I hadn't kept much records of cashier-given foreigns; could be one of the 10-ruble bimetallics, but I have no idea which one specifically).

If you wonder, my Armenian and Serbian visits were both in 2014, I've been to Israel many times but these particular coins were found in 2012, and I think the rest was in 2013 but I don't recall specifically.

Problem with question is no time frame. Remember that some members are old so when they were taking coins out of change, some of those are now called rare or just expensive. For example when I was a kid, I filled my Lincoln Cent Folder with all from change including 09S VDB and 14D and 22 plain. Of course this was so long ago, not many coin collectors around. Roosevelt dimes not invented yet same with many other coins we use today. Way back you could fill an Indian Head Nickel book from change in a matter of days.

I have a few...
1995 ASE
1964 Canadian silver dollar
1867 3-cent nickel

I would say although not the most rare or expensive, a 1938 nickel. Always gets my imagination going trying to think of all the places this coin may have been.

Got a really dramatic nickle error last year, I have found a couple of 64 JFKs, a few Buffalo nickels, merc dimes, silver Roosevelts and one silver Roosevelt proof. Nothing mind blowing but fun stuff!