Inspired by Chain Lightning, I'd like to hear everyone's opinions about spells that are either useless, a pain in the rear, or don't work like they're supposed to.

Well, you can read what a sorcere in my opinion needs to take from the other post. Anything not posted there is either useless or can't be used due to castings needed for the other spells of that class.
Eg. Mirror Image is priority 1 2nd lvl spell, you can't live without it, so it leaves little room for Agannazar's Scorchers and what not.

i always stick to the same ones

if your sorcerer/wizard is on autocast then mirror image and stoneskin are pretty useful. I wouldn't think of casting them otherwise.

some of the higher level ones are pretty pants.

It's down to personal preferance though

Totally useless are those low-level damage-inflicting spells when you have levelled up a bit. That's why Chromatic Orb is all you need from that area. You can do more damage more quickly with a bow than with some of those.

What else? Minor Mirror Image and other lite versions? Can't see a sorcerer picking those, but people do various things.

By the way, a word of warning: guys, you can't unlearn spells. You have to stick to your choice for the rest of the game.