Here's an updated critical miss table. The idea behind it is that fighting should always have a chance of something going catastrophically wrong. I used to play where rolling a 1 just always meant you lost your next turn, eventually this got dull. My last table was a little too wonky -- some results were too fortuitous, and some results didn't really make much sense.
"SO YOU ROLLED A 1"
The attack misses, your turn ends, and…
1 Roll on disaster table below
2 Weapon (or prepared spell) breaks in some minor way (i.e. string snaps, chain breaks, the formula gets criss-crossed in your head), can’t use until you get a chance to fix it (a short rest suffices).
3 Your armor breaks in some minor way, disadvantage to physical checks while worn and doesn’t provide protection until you get a chance to fix it (a short rest suffices; if you're not wearing armor, then it's your clothes)
4 Throw held item 1d10x10' straight ahead
5 Trip and fall prone
6 Hit yourself with the attack
7 Lose next turn also
8 Sprain ankle, speed is halved and dex checks (or anything else involving that ankle) are at disadvantage, recovery is d4 days or until Medicine check DC 12 or a level 1 heal spell
9 Sprain wrist, all attacks and strength based checks at disadvantage, recovery is d4 days or until Medicine check DC 12 or a level 1 heal spell
10 Nothing -- you got off lucky
1 Your miss is so shameful you're now blighted from sight of the gods, no divine magic functions on you and all animals attack you on sight, this can be fixed by performing a ritual obeisance costing at least 1d6x100gp (Under 5th level) / 1000gp (5th level or more)
2 Your armor simply falls apart, it can only be repaired by an armorsmith or similarly skilled person for a fee equal to its original cost.
3 Weapon shatters and sprays shrapnel, you and everyone within 10' takes d6 dmg (if you're under 5th level) / d20 dmg (5th level or more); ditto for spells, and that prepared spell cannot be cast until a long rest.
4 You nick an artery, take d6/d20 dmg at the start of each round and die in 1 minute unless magically healed by a 3rd level spell or higher, or a Medicine check DC 15
5 A random encounter immediately joins the fray
6 Your backpack breaks and your entire inventory falls onto the floor and any fragile items have a 25% chance of shattering
7A level 10 thief backstabs you for d20 + 5d6 dmg, where’d he come from???
8 You critical hit yourself
9 Earthquake! It goes for 1d6 rounds. Everyone has to make a Dexterity save DC 14 immediately or fall down and can't get up until it's over, even if they succeed they can only move at half speed. Within 50 miles buildings collapse, avalanches occur, roads are wiped out, bridges crumble. If you’re underground, then every round you take d20 damage from the ceiling falling. Walls and hallways collapse. 50% chance of tsunami if by the ocean.
10 A raven caws, a shadow passes over you. You may continue your turn, but next time you reach 0 hitpoints, instead of normal 5e death rules, roll on the death and dismemberment table. If you were already going to roll on it, instead roll with disadvantage.