AltFire:
        TNT1 A 0 A_JumpIfInventory("IsInSpawnRoom",1,"Ready")
        TNT1 A 0 A_JumpIfInventory("HasClass",1,1)
        goto Ready
        MISG AAAAAAAAAA 1 A_JumpIfTargetInLOS("AltFireGo")
        goto Ready

CLAW E 0 A_JumpIf(tid==601, 32)

ACTOR LChainsaw : Weapon
{
Obituary "%o was mowed over by %k's chainsaw."
Radius 20
Height 16
Inventory.pickupmessage "Found a Chainsaw."
Weapon.selectionorder 998
AttackSound "weapons/sawhit"
Weapon.preferredSkin "ChainsawSkin"
Weapon.AmmoType1 "Gasoline"
//Weapon.AmmoType2 "Gasoline"
//Weapon.AmmoGive1 1000
Weapon.AmmoUse1 1
//Weapon.AmmoUse2 1
+WEAPON.MELEEWEAPON
+INVENTORY.UNDROPPABLE

States
 {
 Spawn:
 CSAW A 0
 goto Death
 
WeaponDrop:
    TNT1 A 0
    TNT1 A 1 A_TakeInventory("IsDropping",1)
    TNT1 A 0 A_TakeInventory("Slot1Filled",1)
    TNT1 A 1 A_TakeInventory("SawOff",1)
    TNT1 A 0 A_TakeInventory("SawOn",1)
    TNT1 A 0 A_FireCustomMissile("DroppedChainsaw",0,0,0)
    TNT1 A 1 A_TakeInventory("LChainsaw",1)
    LOOP
    
 NoAmmoReady:
    TNT1 A 0 A_JumpIfInventory("IsDropping",1,"WeaponDrop")
     SAWF A 0 A_StopSoundEx("SoundSlot6")
    SAWF A 0 A_StopSoundEx("SoundSlot7")
    SAWF A 1 A_WeaponReady
    SAWF A 0 A_JumpIfInventory("Gasoline", 1, "Ready")
    loop
    
 OffReady:
    TNT1 A 0 A_JumpIfInventory("IsDropping", 1,"WeaponDrop")
     SAWF A 0 A_StopSoundEx("SoundSlot6")
    SAWF A 0 A_StopSoundEx("SoundSlot7")
    SAWF A 1 A_WeaponReady
    SAWF A 0 A_JumpIfInventory("SawOn", 1, "Ready")
    loop
    
 Ready:
 TNT1 A 0 A_JumpIfInventory("IsDropping", 1, "WeaponDrop")
 TNT1 A 15 A_PlaySound("weapons/sawzip")
 TNT1 A 15 A_PlayWeaponSound("weapons/sawpull")
 TNT1 A 5 A_Jump(96, 6)
 TNT1 A 15 A_PlaySound("weapons/sawzip")
 TNT1 A 15 A_PlayWeaponSound("weapons/sawpull")
 TNT1 A 5 A_Jump(96, 3)
 TNT1 A 15 A_PlaySound("weapons/sawzip")
 TNT1 A 15 A_PlayWeaponSound("weapons/sawpull")
 TNT1 A 5
 SAWD E 1
 SAWD D 1
 SAWD C 1
 SAWD B 1
 SAWD A 1 A_JumpIfNoAmmo ("NoAmmoReady")
 TNT1 A 0 A_JumpIfInventory("IsDropping",1,"WeaponDrop")
 TNT1 A 0 A_PlaySoundEx("weapons/sawidle","SoundSlot6",0)
 SAWR ABCDEF 1 A_WeaponReady
 TNT1 A 0 A_TakeInventory("Gasoline", 1)
 TNT1 A 0 A_PlaySoundEx("weapons/sawidle","SoundSlot6",0)
 SAWR ABCDEF 1 A_WeaponReady
 TNT1 A 0 A_FireCustomMissile("LSawSmoke",250,0,20,-5,0)
 TNT1 A 0 A_PlaySoundEx("weapons/sawidle","SoundSlot6",0)
 SAWR ABCDEF 1 A_WeaponReady
 TNT1 A 0 A_FireCustomMissile("LSawSmoke",250,0,20,-5,0)
 TNT1 A 0 A_PlaySoundEx("weapons/sawidle","SoundSlot6",0)
 SAWR ABCDEF 1 A_WeaponReady
 TNT1 A 0 A_FireCustomMissile("LSawSmoke",250,0,20,-5,0)
 Goto Ready + 15
 
 Select:
 TNT1 A 0 SetPlayerProperty(0,0,2)
 TNT1 A 1 A_Raise
 Loop

 Deselect:
 TNT1 A 0 A_StopSoundEx("SoundSlot6")
 TNT1 A 0 A_StopSoundEx("SoundSlot7")
 SAWR A 0 A_JumpIfInventory("SawOff", 1, 1)
 SAWR A 1 A_PlaySoundEx("weapons/sawdown","weapon",0)
 SAWR BC 3 A_TakeInventory("SawOff",1)
 SAWR DE 4 A_TakeInventory("SawOn",1)
 SAWR F 6
 SAWD ABCDE 1
 TNT1 A 20
 TNT1 A 1 A_Lower
 Wait

 Fire:
 TNT1 A 0 A_JumpIfNoAmmo ("NoAmmoReady")
 TNT1 A 0 A_JumpIfInventory ("SawOff", 1, "AltFire")
 SAWF ABCDEFG 1
 TNT1 A 0 A_ReFire
 SAWF GFEDCBA 1
 Goto Ready + 15
    
 Hold:
 SAWF F 0 A_StopSoundEx("SoundSlot6")
 SAWF F 0 A_JumpIfNoAmmo ("NoAmmoReady")
 SAWF F 2 A_PlaySoundEx("weapons/sawfull","SoundSlot7",0)
 SAWF G 2
 TNT1 A 0 A_CustomPunch(0,0,0,"FMSawPuff", 52)
 TNT1 AAA 0 A_CustomPunch(4,1,0,"FMSawPuff", 52)
 SAWA D 0 A_TakeInventory("Gasoline", 3)
 SAWF G 0 A_FireCustomMissile("LSawSmoke",250,0,20,-5,0)
 SAWF F 2 A_Refire
 SAWF EDCB 1
 TNT1 A 0 A_FireCustomMissile("LSawSmoke",250,0,20,-5,0)
 TNT1 A 0 A_StopSoundEx("SoundSlot7")
 Goto Ready + 15

 AltFire:
 SAWF A 0 A_JumpIfInventory("SawOff", 1, "TurnOn")
 SAWF F 0 A_StopSoundEx("SoundSlot6")
 SAWF F 0 A_PlaySoundEx("weapons/sawdown","weapon",0)
 SAWR ABC 1
 SAWR DEF 2
 SAWR ABC 3
 SAWR DEF 4
 SAWR A 1 A_TakeInventory("SawOn", 1)
 SAWF A 1 A_GiveInventory("SawOff", 1)
 goto OffReady
 
 TurnOn:
 SAWD A 1 A_GiveInventory("SawOn", 1)
 SAWD A 1 A_TakeInventory("SawOff", 1)
 SAWD ABCDE 1
 goto Ready

Death:
       DHSP A 0 A_SpawnItem("DroppedChainsaw",0,0,0,0)
       TNT1 A 0 A_FadeOut(1.0)
       goto death + 1
 }
}

Quote from "Torr Samaho"
Can you track this down further with the builds listed here?

actor Zombie_ : Pistol
{
  Weapon.SlotNumber 2
  states
  {
  Fire:
    PISG A 1
    PISG A 1 A_JumpIf (tid==0, 1)
    PISG A 1
    goto Ready
  }
}