My Kingdom for a Horse!

This is from one of my blitz games at the Internet Chess Club. The final position was reached after I played 38... r8f2#. It is displayed here for no other reason than its peculiarity with the four rooks forming a wall around the white king. The black pawns act like a hedge against the white knight. The black king is isolated and vulnerable. You can deduce that it was a slam bang affair, but I got to my opponent before he could get to me.