Some time ago, I threw my PCs up against an orc shaman... he had a whole bunch of levels in Sorcerer, and I'd decided to alter the descriptions (but not the mechanics) of the effects of some of his spells just to change things up a bit. Of course, he had Magic Missile as one of his first level spells. After a few rounds of the PCs tussling with the shaman's bodyguards, the shaman decides to throw a magic missile at the party's heavily armored fighter. I described it like so...
"The Shaman, standing nearly a hundred feet away, mutters a chant and slashes at the air in front of him with an oddly shaped ceremonial dagger. With each slash, you feel a stinging, burning cut drawn deep across your chest. Even though your armor hasn't even been scratched, you can feel the blood beneath it dribbling down your chest and soaking into your tunic. Take... [DICE ROLL] ...12 points of damage."
"Doesn't he get a saving throw?" asks the party wizard.
"No," I reply.
"But you didn't make an attack roll," he wonders.
"That's right," I answer.
"So..." he concludes, incredulously, "It's a spell that did 12 points of damage from a hundred feet away without requiring an attack roll or a saving throw, and it bypasses armor?"
"You got it," I confirm.
"Wow, he says to the other players, "I hope he's got that spell on a scroll or something... I've GOT to scribe that into my spellbook."
Without explicitly knowing which spell it was, and only seeing the end results, the player was boggling... Until I told him that it was just a magic missile, it was a must have spell that seemed too good to be true.