For me along with a wolf standard its a must in every squad of Grey Hunters I use, more often than not you will get a couple of marines attacks out of it and with a bit of luck one or two of them will be rending attacks.
My big problem with it is how to model them, at the moment my marines with MOTW have black shoulder pads and red park markings in reverse of my normal marines however I'm just not that taken with them. I have tried in vein to find the wulfen models that GW made once upon a time but they go for silly money on Ebay so I was delighted with my discovery this morning at Maelstrom games in Mansfield.
Westwind productions make these models as part of their Secrets of the third Reich range and I think they re perfect for those brothers that can be taken by the beast that lies within at any point.
I will post pics of my finished model but until then what do our readers use for their mark of the wulfen models?