Obrigado / Obrigada
Obrigado is what guys say when they're too lazy to say thanks right. Obrigada is what girls say when they're too tired to say it properly. It’s like being forced to say thanks by a toddler who won’t stop crying.
My dad said 'Obrigado' to the waiter who gave him the wrong food.
My mom said 'Obrigada' to the neighbor who played loud music all night.
My brother said 'Muito obrigado' to the friend who forgot his birthday.