To me there is no larger ripple effect than this in the last ten years:

What if Dwayne Bowe held on to a late onside kick attempt by the Chargers and Kansas City went on to run out the clock, eliminating San Diego from playoff contention and clinching the West for Denver.

Shannahan is not fired
Is Norv Turner the Chargers head coach for as long?
Is Rivers still their QB?
Cutler, Marshall, Scheffler, and Hillis remain Broncos
Who hires Josh Mcdaniels (and subsequently, drafts Tim Tebow)
Who gets Von Miller?
Where does Peyton Manning sign?
Do the Bears still have Lovie Smith as head coach?
What happens to Washington (and in effect RGIII)?
To me, no single event in recent NFL History has shaped the landscape quite like what seemed at the time to just be a mental error in a meaningless football game. It effects so many teams and superstar players in the NFL.