Weapons that should be added

[Spodershibe]

https://www.youtube.com/watch?v=qg0RdhFnTd0 (Fat Mac, chambered in necked down 20mm vulcan ammo)
https://www.youtube.com/watch?v=FIU8axpaYi0 (Dual tube dual barrel pump action combat shotgun that holds 6 rounds in each tube and you can selectively pick which one to fire from, allowing you to load each with different loads)
https://www.youtube.com/watch?v=QGKcvM2Hh4g (G11, somewhat infamous attempt at a caseless battle rifle)
https://www.youtube.com/watch?v=98c2t_uK5Uo (and https://www.youtube.com/watch?v=W3IiWjdbUZg, for a carbine to go with the ammo) (Gyrojet, ammo that uses rocket propellant)
https://www.youtube.com/watch?v=X1W8iz8DyRw (Steyr ACR, ACR program entry that shoots flechettes in sabot)
If you are feeling like adding another weird gun, but one that is actually somewhat common worldwide and thus not really "forgotten", the APS (or later ASM-DT) guns would be cool as well
https://en.wikipedia.org/wiki/APS_underwater_rifle
https://en.wikipedia.org/wiki/ASM-DT_amphibious_rifle
yeah

[ChainsawGarden]

Thanks! Will be looking into these later today.

[Spodershibe]

Additional suggestions
https://www.youtube.com/watch?v=-ykmqUFJWAw (AK-53, weird Swiss gun that cycles the barrel forward, among other things)
https://www.thefirearmblog.com/blog/2020/07/08/belt-fed-bullpup-lever-action-rifle-chambered-in-44-magnum/ (UK Legal belt fed bullpup lever action carbine rifle thing in 44 magnum)