The Daiquiri.  A drink everyone has heard of, but likely the many people think of as a pink slushy containing copious amounts of inexpensive nondescript alcohol.
What the Bartending community sometimes refers to as a “Classic Daiquiri” is a very different drink than the slushy artificially colored and flavored thing many people think of as a Daiquiri.  While a frozen Daiquiri can be delicious, a “Classic Daiquiri” is  simply 3 ingredients, shaken until very cold and served without ice in a chilled cocktail glass. It is arguably one of the most important drinks for any Bartender to master. 
This wonderful cocktail, (I start to crave one as I write this at 10am), is a delicate balance of Rum, freshly squeezed lime juice and simple syrup.
Just as the simple omelet is considered a gage of a Cook’s talent, a Bartender’s Daiquiri is a clue into a Bartender’s skill, methodology and education.
What makes this drink so important?  For one, the Bartender must perfectly balance the three ingredients.  Too much lime juice, or not enough sugar and the drink will be too tart and make your face pucker.  Too much sugar and the result will be obvious.  Not enough Rum and the drink will be “flabby”.  As it is shaken, a fourth ingredient is added - water.  Diluting the drink with the perfect amount of water from the melting ice is a technique that takes skill, precision, instinct and experience.
There is another reason that this cocktail is so important for the Bartender to understand and be able to prepare properly.  This drink is a basic “sour” style drink, like a whiskey sour.  Just as the culinary world has 5 “mother sauces”, we have categories of cocktails. The sour is the basis for countless drinks. 
For more details and cocktail recipes please visit bartenderjourney.net/daiquiri