This is an unknown Reaper model from Mass Effect 2 (I wasn't aware there were any more aside from Harbinger and Sovereign actually in-game, and since I have yet to actually see
this, I'll assume it is unused). Found in the BioD_N7Spdr1_500.pcc
Mass Effect 2, Reapers © BioWare/EA.
You are free to use this reference however you wish. You can also download the full size version for a better quality image.
My full list of references can be found here