Foundations

Basilisk Collar

Equipped creature has deathtouch and lifelink. (Any amount of damage it deals to a creature is enough to destroy it. Damage dealt by this creature also causes you to gain that much life.)
Equip {2} ({2}: Attach to target creature you control. Equip only as a sorcery.)

During their endless travels, the mages of the Goma Fada caravan have learned ways to harness both life and death.

Duskmourn: House of Horror Commander

Equipped creature has deathtouch and lifelink.
Equip {2}

A mark of companionship, not subservience.

Fallout

The List

Alchemy Horizons: Baldur's Gate

Some patriars pay massive sums for exotic pets that can give their posh, predictable lives an edge of danger.