Signature cocktails

We have decided instead of having an open bar with lots of drinks choices. We will do beer, wine, sodas, water, and two signature cocktails. A his and hers. Trouble is we are social drinkers and we mainly stick to a few drinks we know we like. How does one determine what the signature cocktails will be. We would like something easy for our bartender and something that will be quick with not a lot of mixing ingredients or a blender. Stir or shaker only drinks.