MK had Ducky 1087 with Green XM ALPs. Those take the win for lightest switches, I challenge someone to find lighter switches.
Fair warning though this keyboard is a pile of stinking crap (besides the awesome feel of the crunchy, hollow, clickity goodness) it's usually warped, switches have varying required force, and the key caps fall apart if you try to remove / replace them.
MK sells the switches sometimes.