Alka-seltzer

Perhaps the best icebreaker ever made. It consists of Taking alka-seltzer, dropping it into a woman's drink, it fizzing, and her asking "is that Roofies?"

You-drop alka-seltzer into cup
Woman- what the fuck did you just roofie me?
You-Pull out alka-seltzer and explain its just that

she might then say something along the lines of "Oh my Gosh that is so funny we should have sex right now"

...your welcome