Molotov Cocktease is a Russian assassin that leads a group of female mercenaries known as The Blackhearts on The Venture Bros.  Molotov has a weird relationship and history with Brock where the two are either trying to kill each other or come close to making love, but always stopping short because of her chastity belt.

She's definitely done friendly things for Brock including watching over Dean and Hank in his abscence, but has also shot him.  So go figure.