is the question 'which athlete' or 'which board member' has the coolest rookie card?...sure I violated the rules by posting non RCs, but those were definitely two of the most desired cards in the early 90s when kids actually collected...
To answer your question, you can go in so many different directions. So here are my top 3
Jim Brown. Beautiful set design and great picture. Probably the #2 most iconic football card.
National Treasures Shield Autos. I am using Luck but could go with any of the big RCs of the NT era and Luck was the first I found. Great clean design and the full shield (especially the old Reebok ones) are gorgeous in hand.
And the "homer"....
2003 and 2004 Pristine Gold Refractors are my favorite set design. 3 different RC card designs (the 3rd of each looks exactly like the veterans and the rookies I have scanned don't look as nice as the vet scans )
Although it is technically his second year card, it is the first card of his own and it has the rookie all star trophy on it. It is also one of the most iconic cards in all of baseball, and I love the action shot.