Fear,Counterspell, Hypnotic Pattern, Fireball, Haste, and Revivify + Spirit Guardians (for the divine soul sorcerer) are just too good.

Spirit Shroud is also great for Martials.

Ashardalaon’s stride is really really fun in the right place as well. Unmitigated fire damage just for using your move speed? Not always worth the concentration slot, but by far one of the coolest 3rd level spells.

I’m a big fan of Plant Growth too actually. But that’s more Bard and Druid.