I can think of a few exploits for spells with low predictable damage.

Clearing a Web with Burning Hands (which would do 1 damage, plus the 1d6 from the burning web)

Dropping a swarm of Stirges with a Fireball. This does require some metagaming since Stirges have 5HP and a Constrained Fireball does 5 damage. You could drop this on the party and they would take minimal damage whilst ending the encounter.

These are corner cases, but there are likely more.