My current campaign is very by-the-book, with minor changes, in no particular order. Note that I run a low-medium level campaign with not much cash for players.
0) Skill Focus -- unchanged
1)
Shield provides no actual cover.
2) When rolling hit points, a player may opt to re-roll once, but must take the reroll. This has led to some 1's (snicker).
3) In a critical hit only the dice multiply, not the bonuses. Too randomly deadly to PCs otherwise.
4) Reduced spell scribing costs of course.
5) Favored-class choices for non-humans (one-time choice), humans and half-elves can choose whatever class is most beneficial to them and switch that around.
6) Unarmed characters threaten -- but then, this is not a house rule
7) Minor fumble rules on a 1 followed by a 1-5 on a second d20 roll. Second roll determines severity of fumble based on my whim.
8) No alchemical items. No locked gauntlets. There are double-crossbows. There are double-weapons and spiked chains but subject to much laughter.
9)
Harm has not come up yet, but it'll involve a save of course.
10) Two characters can fight from the same square. Both of them lose Dex bonus to AC, and may only attack with piercing type attacks or else be at a -4. Possible feat to allay the negative to hit.
I'm considering starting a new campaign with much more extensive house rules... might as well make up a whole new system, though, because I'm not entirely fond of d20...
I'm
very curious about running a campaign with rules more like the Star Wars rules: a defense bonus that scales up with level, Vitality/Wound points, etc.