My US type collection so far (not going to show the very modern stuff):
Half ¢ - missing both subtypes of the Liberty Cap (1793-97)
1¢ - missing both subtypes of Flowing Hair (1793) and the Liberty Cap (1793-96)
2¢, 3¢ - Missing type 3 of the silver 3¢
5¢ - Missing the Flowing Hair (1794-95) and both subtypes of the Draped Bust (1796-1805)
10¢ - Missing both subtypes of Draped Bust (1796-1807) and 6 of the 8 Seated Liberty subtypes (1837-91)
20¢ - Shortest lived denomination is US history (1875-78)
25¢ - missing 1 of 2 Draped Bust subtypes (the 1796) and 7 of the 8 Seated Librty subtypes (1838-91)
50¢ - missing 6 of the 7 Seated Liberty subtypes (1839-91)
$1 - Missing Flowing Hair (1794-95), both subtypes of Draped Bust(1795-1804), and 1 subtype of Seated Liberty (1840-66)