Day 2 - A card with more than one player on it.
I had a hard time narrowing this down to one card so I'm going to cheat on the rules here (assuming there are rules) and feature 4 cards.
1993 Score #512
There are a lot of reasons to love this card. For one thing it features a rare play, the unassisted triple play. For another, it was pulled off by a Phillie. And finally, it wasn't just anybody involved, it was Barry Bonds.
2009 Topps Update #316
Here's the whole challenge list.