Pastel & Pencil
Pastel, be it oil or soft(chalk), allow me to "loosen up". I don't focus as much on the fine detail and simply allow my colours to layer to give shape.
Pencil, well it's my first love. I find the simplicity of their different values relaxing, you don't have to worry about using the wrong colour. This medium really shows your true talents, in my eyes, as painting can hide a lot of our flaws. I know this as I use it to hide mine.