In my first three 4e campaigns I used no houserules, but currently I am running two campaigns that I wanted to feel grittier. So I added house rule sthat icreased the grittiness and added some just for funs sake.
1. Action Point- You can spend an Action Point to gain an extra standard action, to reroll a d20, or to recharge an encounter power.
A player can spend 3 action points to recharge a daily.
I did this because it makes action points more desirable, it makes whiffs occur less often and it gives players a reason to view them as a resource.
2. Injuries - Whenever a character is hit by a critical hit, or is hit by an attack that does more than their bloodied value, is knocked unconscious that player gains one injury. They also gain one injury the first time that they are bloodied during a day. I roll a d12 to determine where on the body the injury occurred (almost entirely an aesthetic thing, but hey scars are badass). Then roll a d20 if that results in a 20 nasty things happen.
For each injury a player has their surge value is worth 1 less.
During an extended rest a successful con or heal check heals 1 injury.
This was done to encourage hunkering down in town for a couple days to heal from all the arrow wounds. It adds some realism and makes the players less invincible. Also some fun roleplay follows when players get scars on their face or maybe loose a few fingers. Things like this become very character defining.
3. During an extended rest players regain 1d4+con mod - injury total. So if a player had a con mod of 3 rolled a 2 on the d4 and had two injuries they would gain 3 healing surges back from that extended rest.
Players rarely have full surges in my campaign and that's the way I like it.
4. If a player or enemy fumbles, they can reroll with a -2 penalty to the reroll at risk of breaking their weapon or implement. If a weapon user rerolls and rolls less than a 10 with a simple weapon, less than a 5 with a military weapon or fumbles again with a superior weapon, than the weapon they are using breaks. Causing it to lose its proficiency bonus and have its damage die decrease by two sizes.
If an implement user rerolls and rolls a critical hit then their implement explodes in their hand causing them to take the damage and the implement to be destroyed. If using a superior implement they get a saving throw after the crit.
5. Armor has an hp-like system which I track, if the armor's hp hits 0 the armor breaks.
6. Dungeoneering is used for crafting. Players can craft or sew or make anything but the time consumed is usually fairly massive.
7.No multiclass surcharge.
8. Linguist only gives one language. but after you have it you can gain an additional language every two levels as long as you have interacted with that culture for an extended period of time.
9. A creature with combat advantage can target specific parts of the targets body. Which I have a table for.
10. A character can use a standard to "focus" or "aim" which gives a +2 bonus to the next attack made on their following turn. Though doing so again make the bonus a +5.
Yup, I think that's all of them.
