Mayo on the Side:

I once knew a fellow who would eat at any greasy spoon restaurant, but wanted NO MAYONNAISE AT ALL, THANK YOU! He discovered that when you order a sandwich with no mayo, you tend to get a sandwich WITH mayo. Then he made a happy discovery: he could order his sandwich with “the mayo on the side.” This instruction would produce a mayo-free sandwich. And he would ignore the little separate container of mayo that had carefully been prepared for him.