Choose your favorite:
On third-and-4 from its own 31 on the first possession of the third quarter, Dallas was flagged twice in a row for a false start. Dak Prescott took a sack on the next play.
The Niners did the Cowboys a solid by roughing the punter on the play after that, but Dallas failed to capitalize.
The next time the Cowboys had the ball, an illegal block wiped out an 8-yard gain on first-and-10. Two plays later, Prescott tossed an interception.
A little while later, an illegal shift negated an 18-yard gain on second-and-20.
On the same drive, after punter Bryan Anger completed a pass to C.J. Goodwin on a fake punt for a first down, Dallas left its special teams unit on the field for several seconds, only to eventually sub in its offense and take a delay of game penalty. Bear in mind that the Cowboys were trailing 23-7 and allowed nearly an entire minute to drain from the clock when this happened. (This might be my personal favorite.)
Trailing by six with just under six minutes to go, defensive tackle Osa Odighizuwa got whistled for defensive holding because he grabbed an offensive lineman on a running play.
Three plays after that, Neville Gallimore's penalty for illegal use of hands allowed the Niners to move the sticks after an incompletion on third-and-12.
Finally, mercifully, the Cowboys ran out the clock on themselves because they didn't realize the umpire needed to spot the ball before they could snap it. "We shouldn't have had any problem getting the ball spotted there," head coach Mike McCarthy said afterward. Alas.