a) Black - frequently

I loved the Intellimouse, and then the Logitech MX510. But - for the last three years, I've been using a Steelseries Sensei RAW (which now has been superseded by the Sensei 310). I love the Sensei as it is perfect for ambidextrous use. It has two programmable side buttons on each side, and a sensitivity change switch on top - which allows you to switch between two distinct "speed" settings. Handy when you are pixel fiddling with images.