Poly sphere. Turn 90 degrees on X-axis. Assign Ramp texture. Use Poly Split Tool to make foot-ball-shaped pupil. Open Hypershade. Create black lambert/blinn/whatever. Select all pupil faces. S-H-I-F-T MYFRIEND - SHIFT-select the lambert shader you just created in hypershade. Right click it. Click "Assign Material to Selection."

Booga!