Thought I'd share the happiness I feel at identifying that annoying and mysterious creak in my cranks! 
Was actually more of a "creak-creak" (one when pedal loaded, one when load removed) noticeable when stationary with brakes on as well as when riding... set up is:
Enduro ceramic EBB, XT M760 cranks, steel Truvativ rings, cr-mo c/ring bolts, Wellgo B-47 flat pedals
I removed all the above then cleaned, re-greased and re-tightened including the BB bearings - still the same creak! :x It was not the pedals as it still happened with none fitted, and the chainring bolts and BB cups were TIGHT! It couldn't be the splined interface between LH arm and spindle as it happened when I loaded either pedal ie just the RH.
I've never had a creak I couldn't fix by removing everything and refitting before... and I've had the exact same parts on two frames with same creak!
Final clue? The creak got lower in pitch when I ran the chain on the outer ring, and higher in pitch on middle and granny rings - could it be the rings themselves shifting about on a different brand of arm? Or - HANG ON! - maybe it's the pin on the outer ring (prevents chain falling between arm and spider) rubbing on the inside of the RH arm?
Whipped it off, filed c.1mm of aformentioned pin - et voila! creak free happiness!
Was actually more of a "creak-creak" (one when pedal loaded, one when load removed) noticeable when stationary with brakes on as well as when riding... set up is:Enduro ceramic EBB, XT M760 cranks, steel Truvativ rings, cr-mo c/ring bolts, Wellgo B-47 flat pedals
I removed all the above then cleaned, re-greased and re-tightened including the BB bearings - still the same creak! :x It was not the pedals as it still happened with none fitted, and the chainring bolts and BB cups were TIGHT! It couldn't be the splined interface between LH arm and spindle as it happened when I loaded either pedal ie just the RH.
I've never had a creak I couldn't fix by removing everything and refitting before... and I've had the exact same parts on two frames with same creak!
Final clue? The creak got lower in pitch when I ran the chain on the outer ring, and higher in pitch on middle and granny rings - could it be the rings themselves shifting about on a different brand of arm? Or - HANG ON! - maybe it's the pin on the outer ring (prevents chain falling between arm and spider) rubbing on the inside of the RH arm?
Whipped it off, filed c.1mm of aformentioned pin - et voila!
creak free happiness! 
