Which brake is most expendable? I'm thinking of removing a brake(front or back) to reduce weight and simplify my bike. Which brake is most expendable? Its your average fixie road bike.
Keep your front brake. It does the most work, it will stop you much faster than your rear brake ever could hope to. Take a look at a motorcycle, the front brakes are always much larger than the rear. Whenever you brake, on a bicycle, motorcycle, in a car, more weight is transfered to the front wheels, so the front tire has more traction to stop you with.

That said, sit down a minute and think about what you're going to do if you remove your rear brake, and one day your front brake stops working while you're going down a hill. Right about then you'll wish you had just put up with the extra 400 grams of weight.