The Desert Eagle Mark XIX appears as the "SOP38 Pistol". Holds 10 rounds in the magazine and can be dual wielded after learning the necessary skill. It is pretty useful even in the later parts too because the game throws lots of weak trashmobs at Sam at later levels.
The Hand Held M134 Minigun, a Serious Sam staple, is present, referred to as the "XM214-A Minigun."
Error creating thumbnail: File missingAirsoft handheld M134 Minigun with 'Chainsaw grip' to handle the recoil force. This variant was seen in Terminator 2: Judgement Day. This is an airsoft version which retains the half-circle attachment point for the M60 foregrip from Predator; the real T2 minigun did not have this - (fake) 7.62x51mm NATOError creating thumbnail: File missingName another game that hands you a Minigun with 1500 bullets and unleashes thousands of enemies at you in the opening seconds...
Barrett M107
The Barrett M107 appears as the "RAPTOR 16mm Sniper Rifle".
Error creating thumbnail: File missingBarrett M107 Long Range Sniper Rifle - .50 BMGError creating thumbnail: File missingDual wielding 2 Barretts because why the hell not? The one on the left is just a mirrored copy of the other one. Part of the ejection port on it should be visible as we can see the start of the mag well. Many other weapons suffer from this when dual wielded.
GP-25
The GP-25 is an unlockable attachment for the Mossberg 590, because it is 2020 and the new Serious Sam game has to have weapon mods, side quests and a skill tree.
Error creating thumbnail: File missingGP-25 - 40mmError creating thumbnail: File missingSam pumping the Mossberg gives a good look of the low-detail GP-25 launcher. This shotgun + grenade launcher combo may seem crazy, but it is nothing compared to the black hole greandes or the gun that shoots heat-seeking high explosive chainsaws.