Brute force or shedding tears by the minute will not get your ex back to you.
If your ex has not been responding to your reunion overtures then a stealth attack in the form of psychological tricks will force your ex to feel attraction towards you and will compel him / her to rush right into your quivering arms.
Get away from the situation for a short time. Both you and your ex could be too emotionally charged up to listen to any reason. A break from an un-winnable situation will help both of you to calm down and compose your thoughts in a logical manner again. This cooling down time will also help you to focus on your entire life instead of simply focusing your energies only on your ex. Your ex could also start wondering about you and possibly even start missing you all over again.
Come back to your own life. When you do come back in your own neighborhood, make sure that you return back to reclaim your life. At least, that is rather the impression that you need to give to your ex. Start working again, get your body in shape by joining a gym and spend your free time amongst close friends. This will divert your mind away from your breakup but more importantly, will puncture your ex's ego and force him / her to think that you just might forget about him / her and move on in life.
Let your ex run towards you. Whenever you do bump into your ex, make sure to talk politely with him / her but do not throw yourself over him / her. Instead, give your ex short glimpses of your improved looks and positive attitude and impress him / her enough for sparks to fly again. Once your ex has been psychologically tricked that you could simply walk away with your new body and improved demeanor, he / she is sure to make all possible moves to win you back. Once the tide has turned in your favor then all you need to do is to wait for your desperate ex to run right into your life again.