Dungeon Master Assistance

This question comes up quite often. There is no official clarification in either the Player’s Handbook or the Dungeon Master’s Guide. Jeremy Crawford said “A non-undead corpse isn’t considered a creature. It’s effectively an object.” But, dead creatures are not simply objects. If they were not still creatures they would not be valid targets for Revivify.
Time for another house rule.

House Rule:  A dead creature (non-undead corpse) can be either a creature or an object, depending on the situation. It is immune to poison and psychic damage, but otherwise can be affected by physical and magical attacks.

As a creature:

• The creature has 0 hit points.
• The creature is unconscious.
• The creature can’t move, hear, see or speak, and is unaware of its surroundings.
• The creature can’t take actions or reactions.
• The creature is not affected by magical or mundane healing.
• The creature is an “unwilling target” for spells that target creatures.
• For any spell that requires an “unwilling target” to fail saving throw to be effected, the creature automatically succeeds on its save.
• The creature automatically fails all other saving throws.
• Attack rolls against the creature automatically hit.
• Any attack that hits the creature is a critical hit.

As an object:  

• The DM determines its Armor Class and hit points. For example: if the object is a dead unarmored human it might have 3d6 Hit Points and an Armor Class of 15.
• The DM might decide that certain dead creature objects have resistance or immunity to certain kinds of attacks.
• A dead creature object always fails Strength and Dexterity saving throws, and is immune to effects that require other saves.

As a weapon, it is an object.

“An improvised weapon includes any object you can wield in one or two hands, such as broken glass, a table leg, a frying pan, a wagon wheel, or a dead goblin.” (PHB p. 147)

As a target for a spell, it depends.

If a spell specifically says it works on creatures, it works on dead creatures.

What the target of the spell can be, as defined in the spell description, determines whether or not a dead creature can be a target for any specific spell.

Some specific spell examples:

Animate Object cannot be used on a dead creature.

Revivify, Raise Dead, Resurrection and True Resurrection all work on dead creatures.

Fabricate “You can fabricate a Large or smaller object …” In this case a creature would not be an object you could fabricate.

True Polymorph has no effect on a dead creature. For this spell, a dead creature is considered a creature with 0 hit points.

Telekinesis has separate descriptions for the target being a creature or an object. For this spell, a dead creature is considered an object.