ESPN's Peter Keating did a recent analysis in an attempt to determine the most valuable sack artist in the NFL. The idea was to chart every sack in the league this season and weight them according to how "clutch" they were. This was done by assigning an expected points saved to each sack.
For instance.... Take a sack that occurs on the opponents 20 yard line vs one that happens on your own 20. Obviously, when a defense gets a sack on their own 20, the offense had been in position to score, so that weights higher. Also, a sack that creates a fumble is obviously weighted heavily as well.
When they compiled this data, Jason Babin came out on top with 26.9 expected points saved. It's significant because the data suggests that Babin isn't racking up meaningless sacks. His sacks are keeping points off the board and coming at significant times.
Certainly the best example of this would be the late November game against the Giants. Down 17-10 with just over one minute to play, Eli Manning drove New York down to the Eagles 21 after a 47 yard pass to Victor Cruz. On the next play, Babin hit Eli from the blindside, knocking the ball loose in the process. The Eagles recovered and the game was over. That's about as clutch as a sack as you can have.