The Beast, here's one I made up a long while back.
RANDOM WEAPON’S FAILURE TABLES
Hand to Hand Melee
Roll 1d20 Result
1 Fall on weapon take appropriate damage. Hand attack, break arm in fall. (GM apply penalties)
2 Suffers a hand wound, causing anything in hand to be dropped reflexively.
3 Tripped, fall down. loose initiative
4 Bad parry, arm stunned 50% chance loosing weapon in hand.
5 Opponent throws/ wind blows dirt/mud in face/face plate. Loose next action.
6 Distracted for that one moment, got clobbered. Stunned for 1d4 melees. Loose initiative.
7 Step in slippery dung. Roll balance check at –30%. Loose initiative.
8 Last hit is catching up with you, blurred vision at –5 to strike for 1d4 melees.
9 Agitated hornet’s nest (in ground or tree). Hornets are attacking all in 20-foot radius.
10 Hand held weapon is stuck in opponent or his gear. If hand only attack, broke 1d4 fingers on impact.
11 Swing so hard with weapon/fist you pull your shoulder muscle. (GM apply penalties)
12 Your anger got the best of you. You go into a rage attacking all living creatures, friends and foes alike, in a 20-foot radius for 1d4+2 melees. –3 to strike, dodge, parry.
13 Swung so hard and missed, weapon went flying 1d20+5 feet away. Hand attack, dislocated elbow
14 Just plain fell flat on your backside. Loose initiative.
15 Bad sprain, lose use of random limb for 1d6 days.
16 Stepped on uneven ground, stumbled, fell with leg under you, dislocated knee. (GM apply penalties)
17 You are just plain having a bad day/run of luck. All your actions for the rest of this encounter are at –5/-20% as per appropriate roll.
18 Swing so hard with weapon/fist you miss and spin around. Back is now to opponent.
19 Your nose begins to get that irresistible itch. Loose one attack/action to scratch.
20 Your attack missed so bad your opponent gets an immediate free attack that you cannot dodge, parry or roll with.
Automatic Handguns, Rifles & Machine Guns Magazine Fed
Roll1D20 Result
1 Explodes
2 Magazine Fell out
3 Did Not Chamber a Round
4 Barrel Splits
5 Hand Guards/Stock Break & Fall Off
6 Fires, Nothing Happened
7 Dropped It
8 Failed to Load It
9 Trigger Stuck
10 Jammed
11 Falls Apart
12 Muzzle End Explodes
13 Trigger Breaks
14 Wrong Caliber Ammunition
15 Forgot the Safety Was On
16 Sneezed Violently as Trigger Was Pulled
17 Loaded With Blanks
18 Hammer/Slide Stuck
19 Ammunition is No Good
20 Out of Control, Fires ALL Ammunition
Revolver Handguns
Roll1D20 Result
1 Explodes
2 Cylinder Fell Open, Bullets Fell Out
3 Cylinder Did Not Rotate
4 Barrel Splits
5 Hand Guards Break & Fall Off
6 Fires, Nothing Happened
7 Dropped It
8 Failed to Load It
9 Trigger Stuck
10 Hammer Jammed
11 Falls Apart
12 Muzzle End Explodes
13 Cylinder Falls Off
14 Wrong Caliber Ammunition
15 Barrel Falls Off
16 Sneezed Violently as Trigger Was Pulled
17 Loaded With Blanks
18 Trigger Breaks
19 Ammunition is No Good
20 Dropped It and Fires on Impact. Chance to hit..??
All Bolt Action Weapons
Roll1D20 Result
1 Explodes
2 Bolt Breaks
3 Did Not Chamber a Round
4 Barrel Splits
5 Stock Falls Off
6 Fires, Nothing Happened
7 Dropped It
8 Failed to Load It
9 Trigger Stuck
10 Bolt Jammed
11 Falls Apart
12 Muzzle End Explodes
13 Stock Breaks
14 Wrong Caliber Ammunition
15 Barrel Falls Off
16 Sneezed Violently as Trigger Was Pulled
17 Loaded With Blanks
18 Trigger Breaks
19 Ammunition is No Good
20 Bolt Lever Broke off
Handheld Belt Fed Machine Guns
Roll1D20 Result
1 Explodes
2 Receiver Cover Pops Open
3 Belt Did Not Feed
4 Barrel Splits
5 Pistol Grip Breaks & Falls Off
6 Fires, Nothing Happened
7 Dropped It
8 Failed to Load It
9 Trigger Stuck
10 Belt Jammed
11 Falls Apart
12 Muzzle End Explodes
13 Belt Fell Out
14 Wrong Caliber Ammunition
15 Barrel Falls Off
16 Sneezed Violently as Trigger Was Pulled
17 Loaded With Blanks
18 Trigger Breaks
19 Ammunition is No Good
20 Out of Control, Fires ALL Ammunition
Tripod Mounted/Fixed Position Belt Fed Machine Guns
Roll1D20 Result
1 Explodes
2 Receiver Cover Pops Open
3 Belt Did Not Feed
4 Barrel Splits
5 Falls Off Tripod/Mount
6 Fires, Nothing Happened
7 Knocked It Over
8 Failed to Load It
9 Trigger Stuck
10 Belt Jammed
11 Falls Apart
12 Muzzle End Explodes
13 Belt Fell Out
14 Wrong Caliber Ammunition
15 Barrel Falls Off
16 Sneezed Violently as Trigger Was Pulled
17 Loaded With Blanks
18 Pistol Grip Breaks
19 Ammunition is No Good
20 Out of Control, Fires ALL Ammunition
All Hand Grenades (Live, Unless Noted Otherwise)
Roll1D20 Result
1 Explodes Immediately
2 Threw Straight Up 1D20 Feet
3 Fell Short of Target, No Damage to Target
4 Pin Already Pulled, Snagged on Your Equipment
5 Dropped it, Rolled 1D20 Feet to Left
6 A Playful Dog in Area Brings it Back to You
7 Threw Pulled Pin, Kept Grenade
8 Dropped it, Rolled 1D20 Feet to Front
9 Went Long of Target, No Damage to Target
10 Fell Apart & Explodes Only Half Damage
11 Dropped it, Rolled 1D20 Feet to Right
12 Was Thrown/Bounced Back to You
13 Partial Dud Only 25% Damage
14 Threw with Pin in (Not Live)
15 Dropped it, Rolled 1D20 Feet to Rear
16 Sneezed Violently as You Threw it
17 Fell Apart (Not Live)
18 Grenade Fizzles, No Explosion
19 Dropped it at Your Feet
20 Dud
Laser Type Weapons
Roll1D20 Result
1 Explodes Immediately
2 Pulled Trigger and Power Source Drains to Zero
3 Barrel End Explodes
4 Did Not Cycle to Fire
5 Barrel Splits
6 Pistol Grip/Stock Break & Fall Off
7 Fires, Nothing Happened
8 Dropped It
9 Failed to Charge/Load It
10 Trigger Stuck
11 Jammed
12 Falls Apart
13 Fails to Fire, Power Overload, Explodes in..??
14 Trigger Breaks
15 Pulled Trigger and Barrel Melts
16 Forgot the Safety Was On
17 Sneezed Violently as Trigger Was Pulled
18 Blinding Flash of Light, Weapon Gone
19 Pulled Trigger, Heating Up Quickly to Red Hot
20 Out of Control, Fires ALL Charges