Like MForceRulz said, this year, your SF pass will get you into Wyandot Lake and The Great Escape, which aren't Six Flags "branded" parks yet. The only non-waterpark I can think of that doesn't accept SF passes is Frontier City in Oklahoma City.
My [free] Six Flags Worlds of Adventure season pass will be getting me into SFMW, SFMM, SFGAm, SFWoA, SFStL, SFKK, SFDL, SFNE, SFA, SFAW, SFoT, SFFT, and SFGAd this year alone. That averages out to about $0.00 per visit. If there's a better deal than that, I don't wanna know about it! Oh wait, yes I do. :)
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"Yes if by crestfallen you mean KILL US!" -- Homer J. Simpson