I'm a combination of Mephista and Dausuul, in this thread.
I've got a player in my group who always plays his characters as (basically) Chaotic Neutral. He's unpredictable at best, and unmanageable at worst. He'll randomly decide to draw a blade on a non-hostile NPC if he's bored (or feeling aggressive), and he'll attempt diplomacy on a creature that the rest of the party regards as a hostile enemy - even if it means foregoing a smart combat action (i.e. "wasting" his turn, and making the fight more difficult for the others). He's ambivalent towards the campaign plot, gets side-tracked by the smallest things, and occasionally makes decisions by throwing a dice. What sorts of decisions? Oh, just small ones... like the character he's playing, which way he'll go in the dungeon, or whether he saves the princess or murders her.
Now, this is just nightmarish to DM. I'd prefer Lawful Evils any day of the week, because at least they have a code, and team spirit (of a sort), and can follow a plan. What's worse is that this player's alignment on his character sheet is almost never CN. It's often LG. The player is just incapable of roleplaying LG, however. It always ultimately ends up back at CN, because that's who he is. And, more importantly,
that's how he enjoys the game.
Fortunately, he's a good guy and we enjoy playing with him. His mad antics have actually made for some incredibly memorable escapades and stories (and more than a few campaign-ending TPKs). But I long since came to Dausuul's conclusion. Alignment is a shorthand tool for monsters and NPCs only. Player characters are different. Whatever they've got written on their sheet is often irrelevant. For an Old School DM like me, that means throwing away all the 70's and 80's thinking of rewarding (or punishing) players who adhere to their alignments. Instead, you simply enforce "consequences" for their actions.
If the dude burns down an orphanage, it doesn't matter if he sees his alignment as LG, CN or NE. Someone is going to be mad. In a Dragonlance campaign, maybe the Knights of Solamnia are going to be sending a patrol to hunt down this criminal. Doesn't matter if the PC thinks he's LG; there are consequences to his actions.
For the record: I'd regard an NPC that acted purely out of greed, and was willing to commit violent or murderous acts, as
Neutral Evil. They don't have much of a code, they're not thinking about long-term consequences, and they have no moral restraints. Evil (to me) isn't about making others suffer; it's about placing your own desires above others. The talk about saving kittens is a smoke screen. The character will save the kitten because it's his personal desire to save it (or he's getting paid to do so), not because it's morally the right thing to do (Good) or because it's the expected or convenient thing to do (Neutral). In my campaigns, any character who is purely self-motivated with no regard for others is at least partially Evil.
...but again, it doesn't matter for PCs. Let the players roll (role?) with whatever they want. Just make sure they reap the consequences.
