big, huge, special
heartfelt
personal
I would just like to say a personal thank you to all the people who contributed to this appeal.

simple

give, say
He didn't even say thank you.
We said our thank yous and goodbyes to the hosts.

get

card, letter, note
He didn't even send a thank-you letter.

thank you for
She got a special thank you for all her hard work.

thank you to
a big thank you to the hospital staff

Thank-you is used with these nouns:
letter, note