I kid you not here... in the Colts game against the Eagles when the Colts were down 9 points and facing 4th-and-18, I was watching the game with my wife She is generally a non-sports fan. Before the play, I said these exact words:
"Watch this. The Colts need to make a play right here or they will surely lose the game. I guarantee you that they will not complete the pass, but that there will be a penalty flag thrown for no good reason, just to keep their drive alive"
Sure enough. Eagles defender Trent Cole’s hand
brushed against Manning’s helmet as he tried to strip the ball. Officials called unnecessary roughness on the play. 1st down Colts. There is a rule that protects the QB from blows to the head, but this kind of incidental contact happens all the time without a flag. Unless it's #18. At the 2:25 mark on this video.
NFL Videos: GameDay: Colts vs. Eagles highlights