In 2006, had two cores to its copper-coated pennys, resulting in some that were magnetic and some not. Combined with the mint logo or its absence, etc., that year produced six variations, one of which is rare (sells for several hundred dollars if the specimen is mint- I won't tell you details, already too many people hunting them).

Now the penny will also disappear, as noted by Little Hawk. Fifty cent coins are rare, so we will have nickel, dime, quarter, $1 loonie and $2 toonie.

The way prices are inflating, I wonder how long it will be before the $5 bill turns into a coin.