The Manhattan is my favorite cocktail, but it's not what I turn to in most situations.
If I'm holding a party, and someone wants a drink and doesn't like beer, I usually make them a Dirty Girl Scout (Vodka, coffee liqueur, irish cream, and creme de menthe. Tastes like a Thin Mint.) It's delicious, relatively simple, and not terribly common (like a screwdriver).
If I'm at someone else's place, and am offered a drink, I generally go with a rum and coke, because odds are they have the ingredients, and it's not complicated to make. If you've heard the name, you know the recipe.
I also really like having a Daquiri (White rum, lime juice, and simple syrup), but I generally save those for when I'm feeling classy.