Probobly the lightest ones your going to find are the Tryall or the Echo drilled rims, the echo only comes in 32H the tryall comes in 32H and 36H. Also the tryall comes in 3 rim widths, the widest is like 42mm which is awesome if your going to be using it for muni.
-- Evan Byrne
"Guns cause crime like flies cause garbage." -Harper
26" alex DX32 is 770 grams and 38.4mm wide, 26" sun doublewide is 875 grams and 45mm wide. It depends on what size tire you're running, anything over 2.2" I would think you would want a double width rim (not the sun, just any of the rims around/over 40mm), I run a 2.3" on a sun rhynolite which is 27.5mm wide and doing larger drops the tire folds to the side sometimes if I don't land perfect. It hasn't come off or blown off yet, but it's not a comfortable feeling. I would say of the two the doublewide is the stronger, although it's also around double the price. I don't know about the smaller brands and their quality/strength/weight. On the plus side, I've done a ton on my 36hole Rhynolite and it's still quite solid, and that's only around 550 grams.