Worrgrendel
Explorer
We use a few houserules at our table.
Hero points: technically not a houserule and more of an alternate rule from the DMG but we use it and like it.
Luck (can't remember what system it's borrowed from): sometimes things just happen out of the blue or are more random happenstance and the DM will call for a "luck" roll, which is 3d6. 6's are good (up), 1's are bad (down), everything else is neutral (even). So for instance a player is looking for something specific in town and the DM has them roll luck for it. They roll 3d6 and get a 1, 4, and 6. This would be even (ups and downs cancel each other out) and the DM determines an outcome based on the roll. 3 up (3 x 6's) is incredible, while 3 down (3 x 1's) is abysmally unlucky.
We also use a homegrown multiple concentration mechanic. Spell casters can concentrate on more than 1 spell based on spell level divided by 3. So once a spellcaster has access to 3rd level spells they can concentrate on 1 spell of up to their highest spell level and 1 more spell of a level no greater than 1/3rd the highest level spell they can cast (rounded down). So a 5th level full caster could concentrate on any spell of up to 3rd level and also on an additional 1st level spell (2 x 1st, or 1 x 1st and 1 x 2nd, or 1 x 1st and 1 x 3rd). A 9th level full caster could do any spell up to 5th level plus a 1st level spell. Once they get access to 6th level spells then its up to a 6th and up to a 2nd (6/3 =2). A 17th level full caster with 9th level spells can actually concentrate on 3 spells, 1 spell up to 9th, 1 spell up to 3rd (9/3 = 3), and 1 spell of 1st level (3/3 =1). My last campaign actually went to 17th level and we never really found this unbalanced things at all (enemy spellcasters can do the same). You made concentration checks on each individual spell.
Hero points: technically not a houserule and more of an alternate rule from the DMG but we use it and like it.
Luck (can't remember what system it's borrowed from): sometimes things just happen out of the blue or are more random happenstance and the DM will call for a "luck" roll, which is 3d6. 6's are good (up), 1's are bad (down), everything else is neutral (even). So for instance a player is looking for something specific in town and the DM has them roll luck for it. They roll 3d6 and get a 1, 4, and 6. This would be even (ups and downs cancel each other out) and the DM determines an outcome based on the roll. 3 up (3 x 6's) is incredible, while 3 down (3 x 1's) is abysmally unlucky.
We also use a homegrown multiple concentration mechanic. Spell casters can concentrate on more than 1 spell based on spell level divided by 3. So once a spellcaster has access to 3rd level spells they can concentrate on 1 spell of up to their highest spell level and 1 more spell of a level no greater than 1/3rd the highest level spell they can cast (rounded down). So a 5th level full caster could concentrate on any spell of up to 3rd level and also on an additional 1st level spell (2 x 1st, or 1 x 1st and 1 x 2nd, or 1 x 1st and 1 x 3rd). A 9th level full caster could do any spell up to 5th level plus a 1st level spell. Once they get access to 6th level spells then its up to a 6th and up to a 2nd (6/3 =2). A 17th level full caster with 9th level spells can actually concentrate on 3 spells, 1 spell up to 9th, 1 spell up to 3rd (9/3 = 3), and 1 spell of 1st level (3/3 =1). My last campaign actually went to 17th level and we never really found this unbalanced things at all (enemy spellcasters can do the same). You made concentration checks on each individual spell.