The big one is replay, which was introduced as a result of a Shawn Jefferson sideline catch during a Patriots-Bills game in 1998.The NFL has made so many rule changes over the years to gin up portions of the game for entertainment value (i.e. passing) that we have lost the meaning of "fair play" in the NFL rules context. What I mean by this is that we no longer refer to a common standard of "catch" or "fumble"; we instead have to collectively navigate rules which we might perceive to be stupid and ridiculous but we still have to be like "well that's the way the rule is written".
That got Ralph Wilson to back down from his virulent anti-replay stance and the rest is history. I thought Wilson was crazy for a while, but I’ve come around to his old way of thinking.