There are many tools that make mixing drinks at home more comfortable and impressive. Soda guns, muddlers, stirring spoons, speed pourers, salt and sugar rimmers and rubber bar mats are all advantageous to have around, but there are two tools you'll need more than anything else.
The first is a cocktail shaker. Without it, liquors go unmixed, tasty beverages go undrunk and thirsts go unquenched. To put it simply, the cocktail shaker is to bartender as horse is to cowboy (or cowgirl). Two common types are the Boston and the cobbler. The Boston shaker is frequently used in bars. It's essentially a large metal cup that covers a mixing glass. This type of shaker is useful for making and shaking drinks quickly with easy cleanup, but you'll need an external strainer if you're planning on making drinks with crushed ice. The cobbler shaker is a little more complicated: a metal cup, a lid with a strainer and a cap for measuring. All parts are useful, but this shaker can be annoying to clean if you're making a diverse amount of cocktails in a short period of time.
The home bartender's second best friend is a strategically placed book of cocktail recipes left open underneath the bar. Nothing's more embarrassing than the words, "What's in a dry martini, again?" and nothing's more impressive than, "A dingo, a black widow and a French 75? Sure, I can make those." Preserve the mystique of the omniscient bartender, even at home.