A classic cocktail is one that has stood the test of time from the 1800's, 1900's to now.
I have several listed on the Classic Drinks All Bartenders Should Know page as well.

 

	Manhattan		Piña Colada
	Cuba Libre		Harvey Wallbanger
	Ward Eight		Presbyterian
	Singapore Sling		Sazerac
	French 75		Whiskey Sour
	Gibson		Rusty Nail
	Between the Sheets		Americano
	Old Fashioned		Bloody Mary
	Mint Julep		Gimlet
	Zombie		Daiquiri
	Bacardi Cocktail		Planters Punch
	Moscow Mule		Tom Collins
	Mai Tai		Stinger
	Screwdriver		Godmother
	Mimosa		Sidecar
	Champagne Cocktail		Negroni
	Bellini

Check out these classic cocktail books!