The usual is either bourbon, brandy or amber or dark rum but if you want one with some pizazz and have the ladies voting you bartender of the year, try this. Make a mixture of cinnamon, nutmeg and just a little turbinado sugar and put that on the rim of a wine glass. Put 4 ozs of the best egg nog you can find in a cocktail skaker, I like Promised Land for store bought because it's not too sweet, add 1 oz of either Amaretto, Frangelico, Grand Marnier and I've even gone half and half with Bailey's and an oz of Kahlua or Tia Maria. The cocktail shaker and straining it reduces some of the thickness and makes it more drinkable to me and people I used to make these for.
Some time back, for a Christmas party, I did a punch bowl of a bottle of Courvoisier and Amaretto plus 4 bottles of egg nog and the guys were laughing at me making a punch and even having a punch bowl set until they started drinking that stuff. I had to make a second batch.