Necromancer
A Necromancer is a kind of magic-user who practices necromancy. "Necromancy" comes from the Greek words nekros ("dead body") and manteia ("prophecy"), and in its strictest sense, refers to the practice of communing with the spirits of the dead to learn about the future. Over the centuries since the coining of the word, its meaning has broadened to include any kind of magic relating to death and the undead, and thus the necromancer's portfolio has also broadened. Necromancers in more modern works are known to reanimate dead bodies, summon ghosts, and drain life-force from the living to fuel their ceremonies (or themselves). Surprisingly, they aren't generally known for fortune-telling nowadays.
Because death is scary, and in many cultures and religions, tinkering with life and death is reserved for the gods, necromancers are generally perceived as evil, and necromancy sometimes inherently so. A common storyline is that a person with magical talent falls in love, said beloved dies, the magic-user dabbles with necromancy to try to bring him or her back, loses sight of the goal, and before they know it, they're turning people into zombies and hamming it up like Skeletor. Some settings are shifting to a more nuanced approach that acknowledge that necromancy, like any skill, can be used for good or evil, but the majority of necromancers are Neutral Evil.
Warhammer 40,000
Warhammer 40,000 doesn't have necromancy per se, but the followers of Nurgle can be like necromancers in many ways, especially when they start breaking out the Zombie Plague.
Warhammer Fantasy
Warhammer Fantasy Battle's magic system features the Lore of Death as one of the eight standard schools of magic. Its practitioners tend to be a little gloomier than most, but the forces of Order are plenty willing to make use of them so long as they kill enemies.