When you are using shield with a throwing knife I have came across a way that is similar to a technique i used in the halo games. When you are playing a non-hardcore game that requires 2 riot shield hits to kill... rather than finishing your primary bash... hit the RB as soon as you are sucked into the enemy. 8 out of 10 times your cross hairs will auto aim to their body standing or to the head if the are crouching. Saves you a lot of time attempting to bash a second time while avoiding getting killed and pisses people off. I use it often and people claim that i have an auto aim Mod since i get so many kills long range and short range.

P.S. The Halo technique i use this with a sniper rifle but hit X and pull the trigger to give me a no-scope to the dome. Auto aim pulls you in for melees and x cancels actions on Halo-2 and Halo -3 i believe