The Green Party MP came to Parliament with a bang in 1999, a dreadlocked Rastafarian who admitted smoking dope and campaigned for it to be legalised.
He said in his valedictory speech that being an MP had changed his life.
"I came to Parliament thinking you're all a bunch of bastards," he told his colleagues.
"And I was wrong. There are many good people here. The very notion that all politicians are dishonest is misconceived."
Mr Tanczos said he believed most MPs came to Parliament with honest intentions, but many were compromised by it.
"How many times have Green MPs spoken in this House and had other MPs sidle over and tell us quietly 'we agree with you'?" he said.
"But they are silenced by their hopes for advancement, promotion, or just to stay where they are.
"The danger is the system changes us as much as we change the system, if not more.
"And that's why I'm leaving. The problem isn't how many people enter this place with honest intentions, but how many leave with them intact."
Mr Tanczos revealed he had avoided question time whenever he could.
"It's a time when I'm most ashamed of being a Member of Parliament," he said. "You all know what I'm talking about."
That was a reference to the abusive shouting and bad behaviour that goes on during question time.
"We should grow up," he said.
"This is our national legislature. We should treat it and the positions we hold with more respect."
Mr Tanczos said the media carried blame as well.
"The buzzards who sit watching us up there, waiting for the next political corpse to pick over ... they will always report a fight but stand to talk about anything real and most of them flap their wings and fly away."
He said the first thing he did when he came to Parliament was buy a watch, and he had been "cuffed to the prison bars of time" ever since.
"So today I remove that shackle, because when I look at the state of our rivers, our atmosphere and our people I don't need a watch to tell me what time it is."
And with that he left the debating chamber, walking over the shattered remains of his watch.
