A600 is pretty much the lightest you can go without compromising functionality, it work like a road pedals as it weighted to allow clip in at an angle.
You can get those Ritchey double sided spd pedals if you're willing to spend a lots of money just to save weight (£100+ for around 230g)
IMHO, stick with the cheap Shimano SPD, pedals weight make sweet fuck all difference.
Edit; by cheap, I mean those M540 pedals that's only about 40g heavier than the top of the range XTR.
A600 is pretty much the lightest you can go without compromising functionality, it work like a road pedals as it weighted to allow clip in at an angle.
You can get those Ritchey double sided spd pedals if you're willing to spend a lots of money just to save weight (£100+ for around 230g)
IMHO, stick with the cheap Shimano SPD, pedals weight make sweet fuck all difference.
Edit; by cheap, I mean those M540 pedals that's only about 40g heavier than the top of the range XTR.