No or No thank you?

[lawrawrrr]

Depends who / what. Usually no thanks, but no thank you if I'm being extra polite!!

[LUCPIX]

Não, obrigado
quite instinctively, by the way -- it'd look 50% uncompleted without the Obrigado

[despect]

I tend to use my manners because that's just how I was bought up. So It's always No thanks!

[Keegan]

I always say no thank you and it's really polite to always use your manners.