Candles
Adding a candle makes any event fancy and festive. In the summer, multiple sets of color coordinating tea lights and lanterns light up the back yard. Our only house lights at Christmas are electric candles. Since working from home, I've burned some tea lights at my desk while working. I even saved up some small glass containers to etch and make into votive holders.
There's just something about setting things on fire that is both comforting and a little thrilling. As a child, I was always horrified when other kids would flick a finger through a lit candle, but I loved playing with the warm wax and lighting matches from candle flames. Lighting the Advent wreath meant the Christmas season had started. Now it's pulling out and lighting a "smelly" tea light that is meant to smell like a pine forest.
Feuerzangenbowle
Of course the country that gave us Christmas trees bending under the weight of flaming candles would also give us a spiced wine punch to light on fire. Technically, the wine isn't on fire, it's the high-proof rum that soaked into the sugar cubes or cone that is on fire, and melting the sugar into the punch below. It's not enough for the sugar to be engulfed in flames, more rum needs to be ladled onto the sugar while it's burning. There's nothing like holding a metal ladle full of flame.
Nothing says festive like lit candles, no matter what the season.