Like what creeper said, it's a great easy way to know you hit a guy. I also use blood patches for this purpose to and yeah, there's always those sick demented people out there :P
BTW creeper, here's a nice blood mod
http://www.modtheater.com/pafiledb.p...on=file&id=105
The mod also has little pools of blood to also let you know that a little fight has been there
