Chemosh, from Dragonlance. Not only a god of death, but also of fatalism.
His most recent work has been seen in the Dark Disciple trilogy, by Margaret Weis. In it, he creates a new group of undead called the Beloved of Chemosh. Chemosh was seeking a group of beautiful undead to sorta give him a new image. Of course, the Beloved have flaws.
There's problems with Kali. Her stereotype is pretty awesome -- drugged up stealthy murderers and street thugs. But her actuality is rather more complex than I usually need in D&D.
I will put in votes for "death mothers," though. Wee Jas fits in this category -- female deities who represent the earth taking life is a cool motif.
I developed a death god for a stillborn supplement named Cettembri. He was a scholar and a historian who carried around a giant tome in which he had the past and future written out. At your death, he would appear with his massive book and check your name off and then *poof* you'd die.
Hel marches her army of the dead against the gods during Ragnarok, just as Voadam said. But they will not help populate the new world. Even though they escape Hel, they remain (un)dead.
Freya is also a goddess of death (in addition to love, healing and renewal; an odd combination, I know), but my favorite God of death is Odin. He's a right sly, old devil! Almost as much of a trickster as Loke. He might seem "lawful", but in fact he only demands that everybody else follows the law -his law. He'll bend or wriggle around the law himself, he thinks he can get aaway with it.