Pushback( Miniatures Handbook, p. 27)
[Fighter Bonus Feat, General]
You can knock opponents back when you hit them in melee.
When you are adjacent to an opponent of your size category or smaller and you hit that opponent with a melee attack, you may immediately make a special bull rush attempt against that opponent. If you succeed, you push the opponent back 5 feet (only) and move into the square (or one of the squares) previously occupied by that opponent. You choose whether the opponent moves one square straight back, one square diagonally back to the right, or one square diagonally back to the left. You can't push an opponent back through (or into) solid obstacles or otherwise occupied squares. If, after making the bull rush attempt, you would not be able to move into a square previously occupied by the opponent, you can't push that opponent back. This feat can be used once per round. The movement caused by the use of this feat does not provoke attacks of opportunity.
A fighter may select Pushback as one of his fighter bonus feats.