You know what's great about having a weekly DnD game at the friendly local game store with guys and gals who aren't you're best buds?
You can be a ruthless DM and not even care. You can keep it 4-realsies DM-style pullin' no punches, and actually feel good about it.
Anyway, check this: In last week's adventure the players were toolin' around the second level of the dreaded dungeon of Thraxdar, and they came across an out-of-the-way door barred from the outside. Like good adventurers they opened the door to peek inside, and saw a huge treasure chest in there alongside a hobbit-sized lizard-skin chicken thing with a long tail eating a crunchy-looking dire badger carcass. The paladin immediately recognized the description as a cockatrice, and informed the party that a cockatrice could turn you to stone with its gaze attack. With that esoteric monster knowledge in mind, they decided that they had enough information to protect themselves and go after the treasure, and the paladin said he would go in and fight the cockatrice.
The problem is that in 3.x DnD it is a basilisk that can turn you to stone (or kill you) with its gaze attack, but the cockatrice turns you to stone with its bite attack. So imagine the poker face I had to endure while the 2nd-level paladin waltzed in to fight the dreaded lizard-bird blindfolded.
This is why everybody makes three characters in my campaign.