spells that you would never want.

[Asmotherion]

like the title says: spells that you see as a complete waste of time and why.
for me it is most blasting/damage spells. yes, even magic missile. why? because direct damage spells take a lot of effort to make worth while, and you are better off doing save or suck in my own opinion.

There are exceptions to this rule, but yeah, generally speaking, blasting is not very well designed.

So practically the few exceptions would be:
-Wings of Flurry for scaling with your Caster Level with no Cap.
-Orb of X Spells and generally any spell that does not allow SR. The best are Orb of Force (for dealing non magical force damage) and then Orb of Fire and Orb of Ice for having feats in their respective elements that allow to overcome Imunity to said Element.
-Magic Missile for it's an excelent spell to put into an Arcane Fusion (Greater) and apply the Fell Drain Metamagic on. Put in an Arcane Spellsurge can drain a LOT of levels in one turn.
-Flame Arrow can be an excelant cheap way to substitute Alchemist Fire (for when you run out of spell slots at low levels) and is spell resistance: no so it can penetrate AMFs and hurt Golems consistantly.
-Vitriolic Sphere. I love this spell; It's practically a lower level Dissintegrade on steroids, and SR: no makes it the only AoE blasting spell I ever use.

But yeah, past the moment I discovered AMFs and Spell Resistance, I've never cast a Fireball or Lightning Bolt again.

I'd also never focus too much on Enchantment and Illusion as schools. Past some level, most things will be Imune to those schools one way or an other. On enchantment, your best bet (if you don't use it as a banned school) is to use it for minionmancy (through Dominate X line) rather than directly in a Boss Fight.