You can use saucy to describe someone who likes to cause trouble, but usually in a playful and funny way. Saucy is also a good word for a person who really likes to flirt.
In the novel Oliver Twist, the character the Artful Dodger goes to court for stealing. During his hearing, the ten-year-old screams, “I am an Englishman; where are my rights?” Saucy words from a saucy child. A saucy comment makes people gasp because it’s surprising and a little dangerous, like talking about witchcraft in front of a priest. Saucy also describes a person who flirts with very sexual language, which can be fun, unless your grandparents are nearby, which is awkward.