Synonymous with a thumbs-up (as it IS a person doing a thumbs up), d(~^_^)z seems to be one of the few emoticons that hardly anyone understands upon their first encounter.
d = thumb
(~^_^) = smile
z = hand or wrist on hip
Bob: Dude, I got two Gatorades from the vending machine and I only payed for one!
John: Nice! d(~^_^)z
John: It's a guy doing a thumbs-up.
Bob: ...I don't see it.
John: Well... *sigh* nevermind.