This is not actually a tutorial. More like a tip. You should know how to make basic custom melee weapon before reading further.
If you played namer720-bunker you might have noticed that when someone is using a knife some strange blinks appear on nearby walls. Those are invisible bullets (projectile model: 15) hitting the wall. Screenshot. To fix this bug you need to make a few changes to the trigger system you used to create melee weapon.
I'll separate triggers by groups to explain:
1) Group 1: triggers that change invisible gun's stats and decoration size.
2) Group 2: trigger that forces decoration to follow invisible gun.
3) Group 3: action on shoot triggers (they make arm offset and change bullet max life).
To fix the bug that appears in namer720-bunker, make following changes:
1) Group 1: gun should spawn 0 projectiles instead of 1.
2) Group 3: add player-specific trigger actions that would change bullet max life to 0 and set gun's projectile count to 1.
*Player-specific action is a trigger action that executes only for player who activates the trigger, but not for anyone else.
*To create player-specific actions, add this before initiating them:
>Set value of variable A to player-initaitor slot
A: (variableA)
B:
>Set value of variable A to slot of current player
A: (variableB)
B:
>Continue trigger actions execution only if variable A equals variable B
A: (variableA)
B: (variableB)
After you set those actions above, you can start changing bullet max life to 0 and setting gun's projectile count to 1. Don't forget to change bullet max life back to 30 and projectile count to 0 with a timer. If you want to see how it works I have added it to my test map. Link.