The third and final Mafia:III DLC is Sign of the Times. It's little more Gabriel Knight or X-files than the standard game, and sees Lincoln uncovering a hidden evil in the heart of New Bordeaux. Not that there wasn't plenty to go around already. It ends with a lighter epilogue that involves restoring Sammy's bar, and finally finding a use for your mountains of late-game cash.
The DLC also upgrades the overall game in two ways. The first is the addition of bullet time to combat.
The other is the addition of Throwing Knives to your weapon menu. These are not available until you've completed the first few objectives in the storyline. While not *much* better than a silenced pistol, knives do have the advantage of being recoverable from enemy bodies. When things get noisy, you can also throw them while still in cover. Their last advantage is that they're invariably deadly- even a knife to the ankle is a killing hit.
There are other rewards as well. Completing the main story arc gives Lincoln access to a drivable hearse (surprisingly powerful, though still more fun than useful), the Motorcycle Club outfit, and the impressive Black Sacrament assault rifle (a modifed Pasadena AR30). During the Renovation tasks you'll unlock the hot-rod Harrier, one of the more muscly cars in the game, and completing Renovation will allow to use the Swamp Hogs and Drink at Sammy's decals.
One special note for completionists- even in the very late game, the enemies of this DLC favor Molotov cocktails- a boon for players still trying to get the Flambe achivement.