I disagree on witchbolt. It has specific uses.
You roll one attack. And then you get continuing, free, auto-hit damage for up to 10 rounds. At d12 per round. No save.
Cast as a higher level, say, third- do 3d12 per round, every round, for up to 10 rounds.
Only the initial damage is increased with a higher level spell slot. The per round damage stays at 1d12.