Ice Breaker vs shield.
Ever since the 1.0.3 update the Hive Knights shields have seemed to change to become an entity themselves. This is because they are susceptible to a fully upgraded Ice Breaker "killing" them in one hit, it causes the explosion effect and the knight seems to not change his animation until it times out. It's possible the explosion still damages the knight however I have not noticed if it does because of the health regeneration effect.
Pulse rifles vs shield
Also since the 1.0.3 update, all pulse rifles seem to be able to shoot straight through the shield as though it is not present. I've tested this with the Praedyth's Timepiece as well as a common pulse rifle on a very low level character.
Not my video, simply shows my point.
Just to follow up for any future reference, this has been patched as of version 126.96.36.199 the hot fix on 12/16/2014.
I have since the patch tested the same weapons as before and proven that they are patched and the reason for this bug originally was because of the Crota's End machine gun's one upgrade being hive darkness shield piercing as well as presumably it's pulse rifle.