For me, I think it's got to be the Long Island Iced Tea. ^_^ There's just something about the complexity of flavor that results that leaves it so desirable.
The mix I'm using today:
Equal measures of:
- basic white rum (Morrison's, in this case)
- London gin (same)
- Curaçao (don't skimp here - Gabriel Boudier's is superb, from Waitrose)
- tequila (here, Aqua Riva reposado - you want a fairly up-front one, not something superbly mellow like Patrón Silver)
- vodka (in this case, Chase, but pretty much anything will do)
Add a shake of lemon juice, ice, and a good dash of cheap diet cola. Yum!