GTW UD-8 Kayser
The Kayser is an advanced primary weapon that is now in its late OpEval period. It has high marks for both shield and armor penetration, beyond even the formidable GTW Prometheus S. Its shots move fast, reach a decent range, and pack a heck of a punch.
That's the good news. The bad news is that, as expected for a prototype weapon, its compatability with existing fighters and bombers is poor. Few craft can mount this cannon. The weapon's energy requirements are also very high.
Still, when you see one of these on the battlefield, you should immediately be very cautious. It's a powerful device, given only to veteran and elite squadrons. Special Operations Command, especially, seems to have priority selection.