Liquid Nitrogen ice cream

The price is about two cents to $2.75 per 100 cubic feet depending on purity, which isn't anything important here, so get the two cent stuff. You will also probably need a container, which you can rent/borrow from the people that you are buying the Nitrogen from. Don't use a cooler, as it will not survive the trip.

Simple rules for handling Liquid Nitrogen:
I could say DO NOT LET IT TOUCH SKIN but someone will be a bone head and do it anyway. The truth of the matter is that the human body is so hot to the Liquid Nitrogen that it will boil in your hand with out any harm to you. However, the instant you contain the liquid Nitrogen, like in a fist, you increase the pressure of the gas trying to escape. The pressure builds up enough to give you a very bad freezer burn. Enough to need medical attention, so take my word for it and don't.

Ingredients needed to make simple Vanilla Liquid Nitrogen Ice Cream:

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Milk
Heavy Cream (Half and Half will do nicely)
Real Vanilla (not that fake junk that's sold!)
Sugar
Liquid Nitrogen

Equipment needed:

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Stainless Steel mixing bowl
Wooden mixing spoon
Gloves
A big sink or a level place out side.

First figure out how much you want to make. Multiply the total amount of ice cream by five to get the amount of Liquid Nitrogen needed to freeze the ice cream. A gallon of ice cream will thus need five gallons of Liquid Nitrogen.
Mix the Milk, Cream, Vanilla and sugar in the mixing bowl. The ratios should be twice as much cream as milk and about 8 tbsp of vanilla for every gallon of liquid. Sugar should be about 1 cup dry measure per gallon. If that's too sweet then half it. I do not know how artificial sweeteners react to the cold, so I don't recommend the usage of them.
Mix the ingredients until the sugar has dissolved into the milk and cream. Add in any fixings (candy, coffee, other flavors). Move to the sink if you haven't already.
Pour in the Liquid Nitrogen slowly and mix with the wooden spoon until completely frozen, which should be about 10 minutes. Wear the gloves, because it's going to be cold.
For a better freeze, prepare the icecream in a pressure cooker, and after adding the Liquid Nitrogen, clamp shut for 5 minutes.

Eat!

If you want, you can add cookie dough or just about anything else to the mixture. Don't worry, it will freeze (trust me, it has no choice but too!).
Other flavors can be made by replacing or adding with the Vanilla with your choice of:
Coffee (hot, strong and fresh is the best) - with a few whole beans - yum!
Cookie dough - either homemade or store bought will do.
Candy - A Milky Way is good in bits, as is Heath Bar.
Liquors - Don't worry about the low freezing point, Liquid Nitrogen is much lower!