The AD&D 2nd edition PHB has an optional table for weapon type vs. AC. While not nearly as insane as the same table from 1st edition, I haven't known many people who have used it, if only because it is jaw-droppingly counter intuitive. The table shows modifiers to the attacker's THACO for using different weapon types (slashing, piercing, or bludgeoning) against the different armor types. This would have worked better, in my opinion, as modifiers to the attacker's to hit roll rather than THACO.
...today, when talking about the table, Mindy and I couldn't come to an agreement. I tried to explain it and she tried to explain it back, each thinking the other was clearly not grasping how this rule was to be used. Finally, she started giving off numbers that were the opposite of mine... +3 was -3. In disbelief, I compared our books... and the tables are reversed. In my book, attacking plate mail with a slashing weapon is a +3 adjustment to your THACO, which is bad and makes it harder to hit. In her book, it's listed as -3. This is the case for all modifiers: +2 in my book is -2 in hers. We have the same version of the PHB (the one with three guys on horseback riding toward you, the 1989 cover I think.) It appears the modifiers in her book are supposed to be modifiers to the actual attack roll, but the text still says they should be modifiers to THACO.
The math comes out the same, if you use her modifiers at penalties or bonuses to the attack roll. The ideas on these tables seem to line up with the modifiers from 1e (slashing weapons suck against plate armor, etc.)
Anyone else ever notice this?