KHE Hindenburg cranks are about as light as they get... 744g
Dont know anyone that uses em so no idea how strong they are
Wombolts/Twombolts 836g Seen several pairs of both broken and the cluster thingy that holds em together falls apart... pretty crap imo
Fly cranks 775g version 1's were prone to snapping, ive had a pair for 2 years now and the only problem i had was waiting 3 weeks for a replacement spindle bolt when mine went awol, they sent me one for free though...
The version 2's are designed better and i dont know anyone thats broke a set
One of the lads we ride with has cracked one arm of his macneil conjointed around the spindle boss, shop replaced it from stock foc, but he's broke every set of cranks he's had and they've lasted about the longest!