I have been using this phrase lately and am quite happy with the results. I always say it as if I've been offered a glass of water and make sure to have a friendly yet slight smile on my face.
My mom: "You shouldn't put that there, it doesn't look nice" said in a condescending tone.
Me: "No, thank you."
The conversation ended there and I didn't get angry.
Coworker: "Tell him to come down here now."
Me: "No, thank you."
She just stared at me, scoffed, and turned away. I could have JADE'd, I could have explained that I wasn't going to tell another coworker to walk 20 yards so the the first coworker could yell at him, but I just politely declined to play that game.
Lady At Grocery Store: "I need that! Give it to me."
Me: "No, thank you."
She said something very not nice to me but I needed the darned thing, too. It's hot and my dogs want to play in the water (I will get pictures up soon! I got them a kiddy pool!)
It's quite nice, this new phrase. Well, the phrase isn't new, but me using it with good results is. I was nervous to use it but it has been serving me well!