The Mai Tai is a classic Tiki drink. You'll need orgeat syrup for this one. Orgeat is a sweet syrup made from almonds (try and get the good stuff--not just the almond flavored--to really take your Mai Tai to the next level).
To make: combine 2 oz of amber rum (some recipes call for a combination of two different amber rums, such as demerara and jamaican, but work with whatever you've got), .75 oz orgeat syrup, .75 oz lime juice, and .5 oz cointreau (or other orange liqueur). Add a large ice cube or several small ice cubes to your mixture and shake to combine ingredients and chill. Fill an old-fashioned glass or double rocks with crushed ice and strain your drink into your glass. Garnish with a tiki umbrella and/or lime wedge. Mai Tai!