Awesome
This is a great game!
My only suggestion for improvement would be a way to win the game or some sort of objective. I really don't like games that go on forever and all you get for your hard work is a score (it's not as satisfying as an ending secquence and credits).
Also, I believe I found a bug. I grabbed an agent, went to the roof of the building and threw him off the side. I then jumped down after him and found he had turned invincible! Anything I attacked him with would go right through, but he could still attack me.