My most unusual find was also my oldest. A 1915 British Large Cent in a roll of halves.
Then there are the usual commemoratives. Booker T. Washington, 1925 Stone Mountain, etc.
Oh, and I found 2 or 3 of the hollow magicians coins.
Back in the "olden times" when TD Bank still had coin counting machines, I used them. When ever I entered the bank, they would walk over to the machine and opened it up. I would dump btwn $2,000 - $2,500 a week. Once I noticed the reject chute was clogged. I unclogged it. Amongst the clogged coin was an 1820 Large Cent. It was in Good Condition. Worth about $20.
In the last box of pennies I opened quite a few of the coins had glitter stuck to them. That box was also unusual in that I found 8 dimes mixed in. Oddly enough, the next day while opening $60 in CWR nickels I came across a roll with 6 more dimes interspersed between the nickels!