Common Spells You Skip
 

Not talking about research spells, dropped spells, or ones via quests but just ones that are available at merchants. I ran into two people the other night who were missing the same spell function and were well past the level where it became available. The omission made a little more sense to me with one than the other but I really wouldn't consider it an option to go without. I'm going to keep quiet about the spell effect to see if anyone else mentions it.

About the only one I can think of that I skip are illusions of the race of my enchanter and the invigor line. Otherwise, I tend to pick up even the spells I consider it unlikely I will ever use, much less being able to resist spells I think are really handy.

True north and if you plan to PL a caster the lesser resist buffs.

Yaulp is the main one that comes to mind for me on a Cleric. As a Shaman I loved having a targeted Yaulp-like spell but I can see how it could be skipped as a Cleric.

As a pally, I would use the yaulp line religiously.
Never made use of the summoned hammer or halo tho...

NARF!

The summoned light sources and clr/pally summoned hammer line. If this was luclin cleric summon hammer is OP.

Summon: heatstone

Dance of the fireflies OP. I had to sell about 12 fire-beetle eyes to get it, but now I can summon a light source any time of day!

Summon food/water as a mage, the stacked versions far outweigh the convenience

I play a human enchanter. I have every single spell for my class, INCLUDING Illusion: Human. :)

My enchanter duos with a wizard and she is missing about half of her spells. Anything involving a light source, vision modifications or the name Al'Kabor and she just doesn't want to know. I think part of the issue is that a human can see perfectly well in the dark, so infravision and light sources are all but pointless.