Good selection of 100% agave tequilas is a must, blanco, reposado, anejo... Cabo Wabo, Dos Lunas, Sauza, 1800, 1921, Patron, etc.
Few gins: Tanqueray, Hendrick's, Bombay Sapphire, Beefeater, Martin Miller, Plymouth, etc
Rums: Angostura, Bacardi, 10 cane, etc
Vodkas: Most of them will do
Triple sec: Cointreau
Also be sure to check various bitters like Angostura or other orange bitters, they really spice cocktails up