The interviewer would like to know if you are the type to set achievable goals for yourself. It's important for the hiring manager to see that you can set personal and career goals and then dedicate yourself to achieving those goals. A career-related goal/achievement is always best.
"This year I set a goal for myself to successfully hire and train three new production workers and ensure an 87% retention rate in our production department. I dedicated myself to training these employees and kept a closer beat in that department. We closed the year at a 94% retention rate, and I was very pleased with this success."
"The greatest goal I set was to graduate University as an honors student while still working full time in a related field. I was top of my class, and working full time. Reaching this goal showed me that I could dedicate myself to my career, and reach the goals that I set for myself. It felt great to accomplish so much and be recognized for my dedication."
"The greatest goal I set was to earn a quality record in my current company. I hit the goal in my first year and received accolades from the VP, which was an exceptional moment. I took a pay cut to move into the role, so to exceed expectations, be promoted, and in turn be financially ahead of where I was previously, was exhilarating."