Quote Originally Posted by Particle_Man View Post
For me it is Prismatic Ray. It is a 5th level spell that only affects a single opponent of 6 HD or lower. I mean, if the opponent only has 6 HD there are probably more efficient ways to deal with that opponent than a 5th level spell slot.

Pity really since it is a colourful spell.
The Blindness part of the spell works on 6HD or lower. The rest of the spell works on any creature.