The flowing bowl. Probably the drink from which all other cocktails originated.
This handy little rhyme will help you remember the basics and you can switch out ingredients as you please. One of sour, two of sweet, three of strong, four of weak. Sour can be lemon or lime. Sweet could be switched out for honey, maple syrup or anything else. Strong is gin (obviously, although rum, brandy and fortified wines work really well and a blend of two or three even better). Weak could be fruit juice, cold tea or water!