You didn't...
Lie?! I'm shocked!
Yeah I did something similar to a rubbish new JVC VHS video recorder (wot thay?

) years ago. After about a week, it began making this very annoying, loud mechanical whistling sound after just a few minutes of use, but intermittently of course and not with all tapes. Why was it rubbish? Very poor user interface, too many bugs and glitches and the recording quality was pants, too. All these goodies from the inventors of VHS. I just wanted to be shot of it.
I'd bought it retail off Currys and they don't take anything back unless it's faulty. Well, it really
was faulty, but in a way that Currys could have been difficult about it and possibly forced me to go home, still stuck with it. So I made sure they weren't. I did the only logical thing I could - made sure it wouldn't power up at all.

No room for argument there.
How?
I carefully unscrewed the cover, took out the internal mains fuse, popped it with a little excess current, put it back in, carefully put the cover back on and handed it back to Currys as "faulty" and demanded a full refund.
The most satisfying bit about the whole experience, was the way the manager was so absolutely, totally sure I'd nobbled it. If suspicious looks could kill... He looked at it over and over, changed power cables, interrogated me as to how, what, where etc it happened and was I
sure, really
sure that I didn't want another?
"No thankyou, I'll have a full refund!" - with a straight face. You could see that he was in virtually physical pain when he had to eventually, finally, satisfyingly, admit defeat and order the cashier to do the refund.
Oh and the icing on the cake? The cashier was new, didn't know what she was doing and messed it up. She ended up calling him over, so he had to fix the mess and do it himself! The manager was livid by the end of that...