Tonight was a vodka gimlet (2 parts Stoli vodka, 1 part Rose's sweetened lime juice) because we were out of ice and the vodka in the freezer was the only cold liquor...
Couple nights ago mixed up a couple of whiskey sours that came out great. The keys: fresh lemon juice and an orange slice + maraschino cherry garnish. My recipe is roughly 2 parts Canadian whiskey (or any mild-flavored North American-style whiskey), 1 part lemon juice, and 1/2 to 3/4 part sugar syrup (depending on how tart the lemon juice is). I say roughly because I don't measure the lemon juice, just figure a small lemon probably gives about an ounce of juice, more or less. The garnishes are key here---while the drink is fine without them, the scent of the orange and cherry really trick your mind into thinking there's more in the drink than there is.
If you've only ever used bottled sour mix, give it a try with fresh lemons (or, in a pinch, bottled lemon juice, preferably the type that includes the lemon oil). It's really a different experience.
