The Minor Pentatonic Scale
The most commonly used scale in blues, rock, and many other styles. Often the first scale guitarists learn, with good reason. A great place to start.
The Minor Blues Scale
The Blues scale adds a single note--the flat 5--to the Minor Pentatonic scale, making it instantly bluesy and awesome.
The Natural Minor Scale
For heavy rock and metal, the Natural Minor adds a classical vibe. It's also known as the Minor Scale or the Pure Minor Scale