No Attack Throws. I use the Target 20 system with an attack bonus progression based on the attack throw progression in a vaguely B/X manner and descending armor class.
Dungeon traps level. They didn't believe I would take their joking comment seriously but the added level of WTF they expressed when the first pit trap was suddenly deeper made it worth it. This will do four things, add WTF, discourage them from trap checking with livestock and hirelings, make it harder for them to metagame a dungeon any replacement characters haven't been in, and it further encourages them to stay in the dungeon longer. Naturally dungeon traps will only level when the players do, which is only after they have left the dungeon and made it to a civilized place for rest.
9 and 30 Kingdoms' Weapon Damage Tables. Well I have them on my screen, but I remembered to use them exactly one time so far. It was on a critical hit. I just need to remember to use them, because they look like fun. The one time I used them the players were all excited, partly because it was a crossbow bolt that ripped through two giant rats killing them both. I'm thinking about trying them out again.
Bum Rush the Titan's D&D Ephemera: 1d4 Tables. I haven't had a reason to use them yet even though I want to because they look like fun.
Firearms. I'm including the Early Modern Firearm rules from LotFP, even though no one has any, mostly because everyone is broke, but also because I sorta forgot to tell everyone. Also, utilizing Brenden S's Firearms Quick Reference sheet. I have also added in proofed armor so firearms don't become too powerful.
Psionics. The 2e Complete Psionics Handbook is the splat book.
Monks. I may or may not make a dwarf monk class.
walking dead aren't villains.
Shadowcasters: Now called the Tenebraeist.
Warpforged: They are like the long lost high tech versions of Warforged.
Octorok : Because my wife is a fan of the Legend of Zelda series.
Moogles: Because I honestly dislike gnomes, but love what gnomes are used for commonly.