Yesterday for no good reason I started thinking about the words we use to indigitate (call, indicate by name) servings of food. The first thing I thought about was the fact that we say 'a slice of pizza,' identifying the serving by the way it generally has been separated from a whole, in this case the pie. So of course I then set out to catalogue and categorize the methods of identification for different kinds of consumables. Just so we're clear, I'm talking about words we use to say "a ____ of [consumable]," excluding the containers they're packaged in and fancy restaurant dish names that specify more than just the nature of the main item in the dish. And so:

Method of Separation From Whole:

Slice - of pizza, pie, cake, bread, watermelon, other fruits
Cut - of (usually red) meat

Of course there are plenty of abstract uses of slice. Some quick lexographic googling shows you can also have a slice not only of life, but also of heaven, being, philosophy, infinity, romance, and Bisbee, Arizona. Mmm...Bisbee. Actually it's impressive how much these uses dominate the google results for "slice of."

Type of Container Served In:

Bowl - of soup, salad, cereal, cherries, pasta, ice cream
Plate - of about anything that is served on a plate, but generally less common with specifics
Cup/Glass/Snifter/etc - of coffee, water, juice, wine, etc.
Bottle - mostly of water or alcoholic beverages, and milk in the olden days
(also Terrine, and other fancy kinds of dishes)

Shape or Part of Whole:

Wedge - of lemon or lime, cheese, melon, lettuce, cake
Scoop - of ice cream

Part of Body:

Leg - of lamb
(Of course there are the many parts of chickens eaten, but I don't think I've ever heard "leg/wing/breast of chicken" rather than "chicken leg/wing/breast")

I feel like a 'shot' of liquor deserves some special mention, because it's not exactly clear what it refers to. Intuitively it seems it might be the method by which one is supposed to consume it, but the OED makes no specific mention of this, and calls it a dram of liquor, which is actually an eighth of our shot. Probably this could go in another category called "real units of measure" or something, which could also include Pint of beer.

There are also some interesting cases where we rarely mention a unit. Dessert beverages: one never has a glass of milkshake, it simply is a milkshake. I almost never say I'm having either a can or bottle of soda, unless I'm ordering one from behind the counter in certain food establishments and have to specify which one I want.

So naturally these were my best guesses at classification, and I encourage others to fill the gaps.