I think my whole collection is comprised of "overlooked" true rookies...at least by my definition, which includes minor league cards, regionals, postcards, etc. And while I love team and multi-player cards, I prefer individual shots/photos.
Here are a few major league cards that fit the bill (last names A-B) - '32/33 Appling, '48 Ashburn, '67 Bench, '47 Berra, '74 Brett, '55 Bunning:
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http://imageevent.com/derekgranger
HOF "Earliest" Collection (Ideal - Indiv): 244/342 (71.4%)
1914 T330-2 Piedmont Art Stamps......: 114/119 (95.8%)
1923 V100 Willard's Chocolate............: 177/180 (98.3%)