Christmas, but I've never really experienced anything else. I vaguely remember the youth group at church when I was a kid discussing the Kwanzaa principles like Umoja, Ujima, Nia etc. around the holidays, but we all still just officially celebrated Christmas; I've never come across anybody that does Kwanzaa. I've never seen a Hanukkah celebration in person, either.
I'm not religious but I love the holiday season and it's really all based on Christmas so I'll say that
im not black so kwanzaa is out and hannukah seems too based in religion where christmas is pretty much a secular holiday at this point