Here's a grapefruit cocktail Mae Clark can thrown right back in Cagney's face!
Paloma
2 oz tequila (blanco or reposado)
½ oz lime juice
7 oz grapefruit soda (or enough to top off the glass)
Add tequila and lime juice to a Collins glass filled with ice. Fill with grapefruit soda (the best is Jarritos from Mexico but sold in many stores and online.)