Standard shaker with built-in strainer, for shaken drinks
Bar spoon, for stirring drinks and pouring floats
Jigger/pony measure, holding 1.5 and 1 ounce respectively
Muddler, for muddling fruit and herbs
Waiter's friend corkscrew, for opening bottles of wine
You don't need all of these tools, though they help. A jigger/pony measure is absolutely essential, as is a corkscrew; a standard shaker is key too.
Float alcohol on top of a cocktail by slowly pouring it over the back of a spoon, with the tip of the spoon gently touching the surface of a drink. Whether it stays floating depends on the density of both the alcohol and the cocktail; gin and bourbon are the least dense and therefore float the easiest; fruit liqueurs tend to be the densest.