A Gin Sour is tasty and simple, and has spawned countless variations. It follows the basic sour format: spirit, citrus, and sugar. Also, It's a great drink to introduce gin to someone who says that they don't like gin. The lemon and sugar do a good job of rounding out the harshness of some gins, but still allow the botanicals to come through.
This is definitely a good time to try out a new gin, maybe your local distillery is doing something cool and using locally grown botanicals.
A fun variation on this drink is the Bee's Knees that uses honey instead of simple syrup.