Looking for the official spelling? Forget about it.
Consensus is definitely for "fuhgeddaboudit." But at least 53 different spellings can be found on the web. As of December 2004, here are the top ten...
What a mobster or gangland figure mightsay to a colleague or business associate, after performing a service for them, they feel obligated to provide for free.
Vinnie the Clam said, "Ah, fuggedaboudit!”
When the assistant DA thanked him for the free Opera tickets!