If you're just starting out on a fixie, you're gonna need a front brake. And even once you get the whole skid-stop thing down, it doesn't hurt to have one in case of an emergency. So why not get a damn good one? Shimano makes some great and affordable calipers and levers. The BR-5600 has proven to have some pretty durable pads and is easily adjustable depending on your riding style. Since you don't need shifters, you can skimp on a lever, like Shimano's compatible BL-R550 levers.
Shimano BR-5600 Brake Caliper
Buy It Now at Tree Fort Bikes, $55
Shimano BL-R550 Brake Lever
Buy It Now at Cambria Bikes, $30