It changes the weapon balance somewhat (so the ammo counts are different), and it allows dual wielding with the pistol, shotguns, and chaingun. It also changes the monster behavior somewhat, and some monsters get angry or desperate when damaged or near death.
-Pistol: Fires in bursts. 2 accurate bullets or hold the trigger longer for 3 or 4 (I really need to organize/improve it).
:::::Alt-Fire: Shotgun ( I should make the SSG possible...)
-Shotgun: More accurate and powerful. In the shotguns, pellets take a fraction of a second to exit the barrel, so you can swing the muzzle across a couple zombies while firing. When using it one-handed, you can cancel the pump (to switch quickly) by pulling the trigger of the other-hand gun right after firing.
-Two-trigger Super Shotgun: More powerful and accurate. Fire 1 shell and reload, or fire two shells in rapid succession. Or after firing 1 shell and it kicks back, center it and fire the second shell before opening it to reload (time your trigger-pulls).
:::::Alt-Fire: Pistol, or the Shotgun if you have one. The dual SSG-Shotgun combo has gotten a bit complex...
-Rapid rocket launcher
:::::Alt-fire: Panic button, block your face with your hand and shoot a close-up rocket when you are cornered. It still hurts, so don't use it when at low health, and your body blocks some of the explosion radius, but the monster who the rocket hits gets more direct damage.
-Plasma Rifle: Less rapid. One shot fires one strong bolt or 2 bolts (watch the muzzle flash). Good for zombie one-shots.
-BFS: Barrel For Spamming, faster than a BFG, less power. New firing behavior and alt-firing planned.
-Imp: Gets angry at half-health, throws 2 small fast fireballs.
-Revenant: Might launch a barrage of missles below half health.
-Arachnotron: Below half health, fires plasma bursts in 3 directions. When death is one shell away, charges up to launch a bigger burst (Invulnerable during charge up).
-Zombies and Imp have enhanced knockback for hitscans.
-Chaingunner and Arachnotron don't fire forever.
-Caco and Pain Elemental can slow their knockback after pushed by a rocket or other attack.
-Lost Souls are weaker, can become Lost Shadows on death (I might ditch this change)
Randy and Graf and ZDoom contributors for all the special lumps.
ID software for the great sprites and sounds
Xaser, Doomrater, Wildweasel, and all those modders who wrote great example code for me to learn from
Ral22 for the smoother SSG animation offsets