Here's some holiday milk shakes. Basically you just have milk, vanilla ice cream, and shots of some liqueur, then mix them in a blender.
Here's a mix that worked for three servings:
2) Ten scoops of ice cream.
3) 1/4 cup milk.
4) Blend on low speed. Just want to mix and not puree.
Grasshopper
The classic Christmas shake, but good on other holidays. Maybe because it's green. Tastes like chicken. Actually mint. Use green Creme de Menthe. You can use the non-green ones but they won't be as holiday-ish unless you add food coloring.
Cricket
Use Sambuca for a clear, licorice flavor.
Firefly
Use some Fireball Whisky for a hot, cinnamon flavor.
Yellow Jacket
The latest one using Eggnog Liqueur. Get this quick since it's usually sold just during the end of year holidays.