I love pretty much every variation of the Kuru Toga pencil by Uni-Ball. I've got the Kuru Toga Roulette in my desk top collection and I have the basic plastic Kuru Togas dotted around the place. I like them because of their single gimmick where the lead rotates as you write, always presenting you with a sharp point.
However, they are far from perfect. For example, the erasers are tiny. I consider them to be for emergency use only and tend to carry a separate eraser around with me. If I want a bigger eraser, then the Pentel Twist-Erase GT gives me nearly 2 inches of extending rubber to erase with. However, it's a plastic pencil, so it feels cheap. Also, the lead doesn't rotate, often leading to a chisel edge.
If I want something that presents with a feel of quality, then the Pentel Graphgear 1000 is a joy to hold. It has an all metal construction and feels perfectly balanced. It also has a 4mm metal sleeve, which retracts when the clip on the side is pressed, thus making it pocket friendly (the Twist-Erase GT also has a retracting tip but the action isn't as smooth). It also just feels like it will last a lifetime. However, the eraser is tiny and the lead does not rotate.
If it weren't for the fact that Kuru Toga invented this rotating lead thing, it'd be tempting to just stock up on Bic Matics. If you shop around on Amazon and buy them 12+ at a time, then you can get them for around 30-40p each.
What does everyone else think?