D-44 85mm Divisional Gun
What, an AT gun? isn't that a Second World War thing?
Believe it or not the USSR still used this sort of gun as a stop line defence. Never supposed to see the main line of battle, this style of gun lurked in the rear line and right now is seeing action in several places across the globe. They would be carefully sited for oblique fire and dug in with a security element and most importantly belts of minefields. Notably it was calculated that weapons in this class like the "Rapira-3" ("Rapier-3") cost 05% as much as similarly armed MBT (note that the 125mm Rapira-3, although not the 100mm "Rapira", and the 125mm Sprut-B were never really adopted for service and only made in small numbers. The vast majority of this sort of gun was either the 85mm D-44 or the 100mm MT-12 anti-tank gun (2A29), a heavier weapon)
The D-44 is a strange gun, it's an actual field gun. This means that it is optimised for both direct fire and indirect fire. It's also extremely obsolete, the last MBT it could penetrate everywhere frontally was the US M47 (which had really terrible armour, like only 200 BHN) and that old warhorse was retired in the early 1960s.
What makes this gun so significant is that it was the primary training gun of the Soviet Bloc. Everyone used this gun or similar versions to train their gun crews, and as such there are simply buckets of them. 10,800 of them to be exact. And as such they still see combat to this day and they're still churning out ammo for it. This means there's tons of them to appear in the AO when more sophisticated weapons disappear through attrition.
The D-44 is actually a viable weapon in Twilight 2000 as apart from the odd rare MBT that someone somehow manages to haul about it only has to face IFVs, APCs and Light Tanks, something it can easily demolish. It's no heavier than the Second World War Wehrmacht 7.5cm Pak 42 yet it develops much more behind armour effect. What makes this weapon distinctive is not only is it comparatively mobile but it is physically small for such a weapon, it's only 1.42 metres (4 ft 8 in) high. Tactically that's tiny. This thing can be dug in with it's barrel not far off the ground in an earthwork and be almost invisible, and this is probably where it will turn up. Note that even thermograph has trouble seeing positions like this.
Mass: 1,725 kg (3,803 lbs)
Length: 8.34 metres (27 ft 4 in)
Barrel length: 4.7 m (15 ft 5 in) 55 calibers
Width: 1.78 metres (5 ft 10 in)
Height: 1.42 metres (4 ft 8 in)
Crew: 8
Sights:
- OP2-7 daylight sight
- S71-7 and PG-1 indirect fire complex
- APN-3-7
"Yablonya" passive/active infrared (note that the IR illuminators are not always attached to the weapon but tripod mounted supplementary units that complemented the system may be some distance from the gun itself. This can cause confusion in attackers as illuminators are switched on and off as tactical requirements require.)
- DAK-2M laser rangefinder
- Some batteries may have the PSNR-1 portable ground reconnaissance radar station (10km)
It's usually deployed in three-gun platoons, two of which comprise a battery. It's tractor is the ubiquitous MT-LB fully tracked vehicle and it is accompanied by other MT-LBs as ammo carriers and command vehicles, otherwise they'll use various trucks, usually the Ural 375 or older ones like the GAZ-66.
Why mention this dinosaur?
You can do a "Guns of Navarone" scenario for these or other AT guns. A friendly group has to pass by some area dominated by these weapons, which are of course immobile and dug into a trench system complete with firing positions. The friendly group is being chased by some overwhelming group so they have a strict time limit. The players must infiltrate and destroy the guns before the friendly convoy passes. This can be the bit where the players get separated from their unit and head off into Poland for further adventures. I know, it's a lot of waffle just for one little scenario idea.
http://www.pmulcahy.com/misc_pages/lgcal_guns.htm
https://en.wikipedia.org/wiki/85_mm_divisional_gun_D-44
(Note that the images are of practice formations. You'd never see them in battle like this. The last image is of a WW2 Soviet light AT position for reference)