The wheat pennies are nice. Both because I like the design, and because they're infrequent enough to set aside into their own pile to check for rarity. I don't bother to examine most cents too closely because it'd take too much time, but I'll do it with the wheat pennies. A bunch of valuable cents might get by me because I'm just hunting for copper, but something ultra rare like a 1943 struck on copper won't.
@Hoss “Cyber Jester” Delgado I'm not too familiar with rare pennies but I remember there being some that worth a pretty decent amount. 1909 S comes to mind.