Im pretty new to this forum but have some previous experience, just want to share a few of these weapon ID's.
A few of these may make your game crash, or glitch. But are often just special weapons.
I have only tested these on The Shadows of Evil. Cant guarantee workingness on The Giant. Will test later.
The Shadows Of Evil:
101 - Wunderwaffe DG-2
102 - Wunderwaffe DG-3 JZ
2 - Vesper
4 - VMP
6 - Bootlegger
7 - Kuda
9 - Pharo
11 - Weevil
13 - Razorback
15 - Crocuta (Pack a Punched Kuda)
17 - Whispering Regurgitator (Pack a Punched Vesper)
19 - Infurnace (Pack a Punched)
22 - Impaler (Pack a Punched VMP)
24 - Barage (Pack a Punched Pharo)
26 - Ein Sten (Pack a Punched Bootlelegger)
27 - ICR-1
29 - KN-44
31 - M8A7
33 - Sheiva
35 - HVK-30
37 - Man-O-War
39 - Annoited Avenger (Pack a Punched KN-44)
41 - Illuminated Demonator (Pack a Punched ICR-1)
43 - High Velocity Kicker (Pack a Punched HVK-30)
45 - Dread Armarda (Pack a Punched Man-O-War)
47 - The Unspeakable (Pack a Punched M8A7)
49 - Columus Struggle (Pack a Punched Sheiva)
51 - KRM-262
53 - 205 Brecci
55 - Shoeshining 100 (Pack a Punched Haymaker)
57 - Dagon's Glare (Pack a Punched KRM-262)
65 - Gorgon
75 - Locus
88 - Starting Pistol (forgot name :P)
The Arbgwaoth Family!:
125 - Kor-Maroth
126 - Mar-Astagua
127 - Nar-Ullaqua
128 - Lor-Zarrozor
129 - Kor-Maroth Arbgwaoth
130 - Mar-Astagua Arbgwaoth (better kor-maroth, i think)
131 - Nar-Ullaqua Arbgwaoth ( i dont even know anymore)
132 - Lor-Zarrozor Arbgwaoth (fml)
139 - Ray Gun / Porters X2 Ray Gun (Pack a Punched)
138 - Ray Gun
The Giant
Take any gun above, and take away 1 from the value.
e.g 11 = Weevil, so now its 10 = Weevil.
(sometimes, atleast. try both.)
33 - HVK-30
35 - Man'O'War
51 - 205 Brecci
57 - BRM
75 - Drakon
96 - Wunderwaffe DG-2
97 - Wunderwaffe DG-3
4150 - Ancient Messenger (Pack a Punched Argon)
364558 - Crucuta (Pack a Punched Kuda)
364587 - Dread Armada (Pack a Punched Man-O-War)
This is due to be edited at any time. Keep checking back for updates,
This took me a while to get, so if this helped, leave a thanks and a comment with any more confirmed ID's