Harry: (some are inappropriate)

-Babe

-Sweetheart

-Darling

-Kitten

Liam: (anything adorable)

-Love

-Honey

-Pumpkin

-Sweetie

Louis:

-Baby

-Carrot Cake

-Sweet Pea (but he only calls you that when he wants something).

Niall: (anything that is sweet or involving food)

-Princess (of course)

-Cutie

-Cupcake

-Sugar

-Honey Bun

Zayn:

-Boo

-Beauty

-Beautiful

-Hun

-Baby

-Doll (occasionally)