Rabulias
the Incomparably Shrewd and Clever
GI Joe could use d20 Modern.
There was always the thought that this would have been a no-brainer, what with Hasbro owning both GI Joe and Wizards of the Coast....
At any rate, Crafty Games made one for Spycraft rules: Real American H.E.R.O.es
And Vigilance Press has turned out some GI Joe-inspired characters in their Wargames supplements for ICONS (sample)