When the DMs interpretation of alignment differs from the players

[(Psi)SeveredHead]

Depends on the party composition as well. In our campaign the Cleric and Pal/Sor use Holy Smite and Purified Fireballs to good effect when the rest of the PCs is in melee with the baddies.

Uh huh... reminds me why I don't like those spells. I'd rather have an Exorcism spell that damages undead and evil outsiders.

Suddenly blasting your fellow PCs would not be a welcome change.

It would if I were behind the DM screen That would remove a lot of mysteries a mysterious NPC might bring with them.

We had the problem with shifting alignment as well. Would a fellow PC be suddenly incinerated by a Purified Fireball after shifting from good to neutral after several levels?

Make him take less damage from it

Or your cleric who has just shifted from LE to LN and finds a Book of Vile Darkness. So now reading the book jolts him?

Bad example. If you're using an artifact like that your campaign already has big problems.