I'm lookin for a strong rim that is good for dirtjumping the ocassional downhill that won't buckle within a week of doing dropoffs:
It's between
-Atomlab Aircorp
-Sun singletrack
-Mavic d521cd
Which are that strongest?

Any of them, just make sure the wheels are built properly. The strongest rim in the world won't last five minutes with slack spokes...

out of the three you've said i would reccomend the Atomlabs. Ive knackered 521's before now but Halos and Atomlabs stand up.
Oh and agree with mike totally, a shoddy wheel build is not a good thing.

Halo combats!!

they are tough as old boots and look funky.

anyone know any body with sun singletrack rims, what r they like?