The more I read SEAL Team 666, the more my mind churns out ideas for using it as a setting. I've started a thread on RPG.Net asking about system and the biggest contender right now is an unreleased product from DWD Studios (makers of the excellent BareBones Fantasy RPG).
That game is Covert Ops and it's apparently in editing. Hopefully we'll see it released in the next few months.
I'm pretty stoked about giving it a go.