More than likely the 1944 matte proof penny. It was stuck in steel instead of copper.
By far the most valuable Lincoln cent is a 1943-D coin struck in error on a bronze blank instead of a steel blank. As of this writing (2015) it sold for $1.75 million.
Online penny auction gives you advantage of purchasing quality and branded products under the most affordable price.
The rarest and most valuable Lincoln cent that isn't an error is the 1909-S with VDB on it. The rarest and most valuable error Lincoln cent is the 1943 copper penny.
1970-S
The One Penny Black is the first stamp created. Most dealers will have them for sale. You can also find them on auction sites as well.
The 1964 Lincoln penny is unfortuantely worth 1 penny. This was not a key date amongst pennies. Most valuable pennies were wheat and Indian head cents dating from 1859-1958
The most expensive Canadian cent is the 1936 DOT, it sold at auction for $402,000 and there are only 3 known. I will add a link to the auction when it sold in January.
At least for Lincoln cents, the most valuable by far is the 1909-S VDB.
1943 copper penny
The highest price ever paid for a car at auction was $11 million paid for a 1931 Bugatti Type 41 Royale Sports Coupe sold by the auction house Christie's in 1987.
The US one cent piece (penny) has the portrait of Lincoln on the "face" of the coin. The obverse (back) pictures the Lincoln Memorial. Both are connected to one of the most revered US Presidents.
There are good and bad penny auctions sites which is why it is important to do research and read reviews from other people. Popular penny auction sites such as swoopo.com have a lot of people bidding which makes it more difficult to win. Other penny auction sites such as Zeekler.com have less people, but have been around a lot longer and because there aren't as many people bidding, it's sometimes easier to win something. I am a rep for Zeekler and by far it is one of the most reputable penny auctions tbinnovate.zeekler.com