Holiday lights would have to be my choice. They can be used on trees, of course, some even decorate Thanksgiving trees, but they can also be used on wreaths, windows, doorways, mantles, stair rails, and throughout rooms, and around outdoor spaces. When the lights go up a festive spirit is in the air!
The Christmas tree and the family ornaments. It is the physical center of our holiday season (meaning other activities take place near it, we spend time together decorating and admiring, of course presents go under it too). The ornaments go back to my grandmother's own first ornament. Every year as we hang them and go, "Oh, this one is my favorite! But I also love this one. And remember when...?" it's like narrating family history.
Lights are essential holiday decor to me too. And I adore miniature villages. Hanging Christmas cards around the door. Setting out nativity scenes. But ultimately the tree is what simply can't be missing.
I just started using Chalk Couture -- you can erase and make amazing signs and holiday decor with it. It makes creating home decor for the changing holidays easy. I think starting with a beautiful table is always essential for a cozy holiday dinner. You can check out more about chalking from my hub profile.