"Grab your lip-gloss and your pepper spray, sweetheart. Your date's here."
-Keith Mars
Cans of Pepper Spray are popular self defense weapons meant to strike an assailant's eyes to temporarily blind or hinder the attacker's vision with painful gel that will cause a feeling of in their eyes that feels like they're being burned.
Pepper Spray wasn't widely used in the series and was instead only referenced or seen for a brief amount of time. Perhaps its most prominent use was in the film when Veronica used it in conjunction with her Stun Gun to briefly incapacitate Cobb and escape Gia's apartment.