An effect wherein any otherwise logical or reasonable argument becomes invalid simply through the referencing Nazism, the resulting imbroglio and fevered invoking of Godwin's Law thus rendering productive debate impossible.
Person 1: Your political agenda seems to hold many direct similarities to the politics of the Nazi Party in pre-WWII Germany, doesn't that concern you?
Person 2: ZOMG!! Godwin!! You are mean, and crazy!!!
Person 3: Yeah, dude...I agree with you, but you can't call someone a Nazi! WTF?!?
Person 1: But...it's a valid comparison!
Person 2 & 3: You just called people Nazis! GTFO!!
Person 1: Fucking Godwin Effect!