One was when I was living in San Francisco and my son visited for Christmas. I don't recall exactly how old he was, I think he was about 10.
He'd been born in Baton Rouge, and was living in Baton Rouge, but we'd lived in Chicago when he was 3-4, that's where his mother and I divorced and she later moved back to Baton Rouge with him. He mentioned that he didn't remember anything about Chicago and didn't remember ever having seen snow at Christmas.
So, I decided I was going to give him a White Christmas. Christmas morning we (myself, Robert (my son), and Terry (my girlfriend at the time) rented a car and hit the road headed East. We took hiway 50 out of Sacramento, through Placerville and along the southern route around Lake Tahoe. We took our time and got to South Tahoe with no reservations and weren't able to find a room at any of the ski places on the California side of the lake, but did find a room at a casino hotel on the Nevada side. We spent a day having snowball fights and drove back to Sunny San Francisco after one night.
I remember us all having a good time. I also remember my ex-wife throwing a fit about it when Robert got home and told her about him having walked through the casino to get to our hotel room. She thought that exposing him to such sin was going to ensure his place in Hell, or something like that. We had a good time anyway.
The other memorable Christmas as an adult is when I was living in East Texas and my girlfriend (Gwen) and I decided to go to New Orleans for Christmas. We drove over with no hotel reservations and found a little place in the Quarter. We had Christmas dinner at a French Quarter bar that off of Bourbon a couple of blocks and was mostly frequented by locals. They were having a pot luck dinner, with various dishes brought by customers and shared. A lot of homemade dirty rice and etouffee. Cafe de Monde was closed that Christmas day. I'm not sure why. But we still had a really good time.