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Who needs Agonizing Blast?
As a player I would like to use a cantrip other than Eldritch blast, originally I would just like an option to use primal savagery effectively and thus I made some ideas and ended on the one below. I then decided to make some more for other cantrips.
Because Agonizing blast approximately doubles the damage of eldritch blast, I have gone for doubling each cantrips potential damage.
Eldritch Savagery
You can choose to replace one of your cantrips with primal savagery. When you use your action to cast primal savagery, you can also cast it as a bonus action on the same turn.
Pitfire
You can choose to replace one of your cantrips with create bonfire. When you cast create bonfire you can create two 5-foot cubes rather than one.
Coldsnap
You can choose to replace one of your cantrips with frostbite. When a creature fails it's saving throw against your frostbite it takes damage from the cantrip again, if it makes an attack before your next turn.
Distracting Buzzing
You can choose to replace one of your cantrips with infestation, and if the direction the target should move is blocked, reroll to try another direction.
Additionally the movement forced by infestation provokes opportunity attacks.
Lightning Chains.
You can choose to replace one of your cantrips with lightning lure. When you cast lightning lure you can choose a second creature which must be within 15 feet of the original target, the original target then moves 10 feet towards that creature if it fails the saving throw, and then suffers damage from the cantrip.
The secondary target must succed on a dexterity saving throw or suffer the same damage as the original target.
Reverberating Force
You can choose to replace on of your cantrips with sword burst, thunderclap or word of radiance. When you cast one of these cantrips, you create a 15 feet cube centered on yourself infused with magic from the spell. Until the beginning of your next turn, each creature other than you that ends it's turn inside the area of moves into the area must succeed on a dexterity saving throw, or take damage as normal from the spell.