You’re being attacked: Roll for defense!
Who doesn’t know this situation: as soon as the fighter has made their attacks and rolled for damage, they pull out their phone and start scrolling through the latest posts on social media. Well, outright banning phones at the table isn’t always an option, since many players use them for character sheets and/or rulebooks. So, what about this simple and exciting house rule: Roll for AC! Your AC isn’t a fixed value anymore , it’s AC − 10 + 1D20. So, a PC with an AC of 16 now has 6 + 1d20 instead and they have to roll it, every round when they get attacked. This makes combat more exciting and feels like you’re actually fighting, fending off enemy attacks. Especially in 1-on-1 combat, it really feels like dueling, and more "realistic". It can also be extended to Spell Save DCs (DC − 10 + 1D20). Moreover, it gives you some wiggle room to add extra effects when rolling a natural 1 or 20 (like dropping your weapon, granting advantage/disadvantage on the next attack, etc.). But first and foremost: This rule helps keep players off their phones! So, what’s y’all’s opinion? Would you try it? Have you tried it already? Let me hear your experiences! Additionally, disarming should be improved. So, a creature provokes an Attack of Opportunity when it picks up a weapon or Arcane Focus. Otherwise, since picking up an item is a free action, disarming is mostly useless. You could also grant a reaction to kick away a dropped item when you're within 5 feet of it.