Well, well, well. Driver Nephi. Nothing to say, you son of a bitch? No tips on my golf swing?”— Major Dhatri
After killing Driver Nephi, his corpse can be searched and his head taken, which can then be delivered to Major Dhatri for a reward as part of the quest, Three-Card Bounty. If his head is shattered while killing him, Driver Nephi's mangled head will be in its place, which serves the same function in the quest, but yields fewer caps as a reward.
If his corpse is not immediately looted, it will remain where he died available to be looted at any point later in the game.