It's hard to choose the nicest thing anyone has ever said or done to me.... lots of things come to mind.
One of the sweetest things someone has done for me is my old boss and adopted dad agreed to walk me down the isle at my wedding.
When my husband and I went to visit a really good friend of mine was battling cancer in the hospital she looked at my husband before we left and said "You take really good care of my girl. She is the daughter I always wanted." She passed away shortly there after but it meant a lot to know that my feelings for her were in line with how she felt for me.
The other nicest thing is my realtor who I have only known a short time but is a kindred spirit if he sold me a house with a pink bathroom he would come and paint it (I am not a fan of pink). Needless to say he was true to his word...painted the bathroom and kept coming back for many days to help with the rest of the renos required to make our place livable.
Cheers,
BReal