Originally posted by Cash D'Money:

I made this by testing each individual weapon and comparing them to their Ultrakill counterparts or to the wiki.
I already mentioned this in the comments of this mod but this seriously impresses me a lot, I wasn't expecting this mod to have carried over so many actual Ultrakill things (such as the nukes, airshots, and more) all while working so well. And while there is a lot of stuff listed, most of it is things I'd consider small that don't drag down the mod by much at all, only improvements to bring it closer to the original game.
The format lists issues shared between all variants of a weapon type, then below that problems with the individual variants.

Universal Feedback

The weapon damages are pretty wack, some instakill and other hardly do chip damage. While there is a meter to adjust weapon damage it affects all of them instead of specific ones, I suggest either adjusting the weapon damages to be proportional to how they are in Ultrakill or give each weapon their own slider. If you don't know how much damage they do in Ultrakill, you can ask me in the comments.
Many explosions also seem to lack self knockback.

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Revolvers

Firing speed might be a little fast though it's hard to tell since both shoot fast to begin with, just in case it is too fast the firing speed is 0.5s in Ultrakill, so 2 shots per second.

Piercer

Pierce shot lacks a cooldown, in Ultrakill the cooldown is 2.5 seconds.
Pierce shot doesn't pierce through enemies.

Marksman

Works perfectly.

Sharpshooter

It's hard to say how this one is working due to a lack of tracers, but it seems to work properly aside from a bug that I'll put in the bugs forum.

Alternate "Slabs"

Doesn't exist so no feedback.

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Shotguns

Firing speeds are too fast, since the variants have different firing speeds I'll write the cooldowns in their categories.
It's a bit tough to projectile boost and the explosion caused is too small, it should be the same size as a Core explosion.
Sometimes the pellet hitboxes are inconsistent, occasionally going through enemies without killing them.

Core Eject

Firing speed should be 1.25 seconds
Secondary fire cooldown should be 2.3 seconds
Primary and Secondary fire cooldowns should be linked.
Cores seems to explode on contact with the player.
Cores can be punched with the feedbacker, boosting it and making an explosion in your face. Honestly I don't mind this, it's kinda cool if you think really hard.
Cores explodes when hit by projectiles when it should only explode to hitscan.
Cores don't despawn after exploding, instead they keep going. This allows for a scary combination when used with the explosion with projectiles thing, you can cause one magnum ♥♥♥♥ of concentrated explosions by shooting a core with the shotgun.

Pump Charge

Firing speed should be 0.92 seconds (that's extremely specific)
There's no cooldown between pumps, so you can spam it to instantly reach full charge. While there isn't a cooldown listed on the wiki, I think the cooldown should be around 0.3 seconds.
Primary fire and pump cooldowns should be linked.
Pellets should have greater spread on higher charge level.

Sawed-On

Doesn't exist so no feedback.

Jackhammers

Hammer takes too long to pull back, it should be a 0.5 second wait to fire with a 0.5 second cooldown.
There should be a 7 second cooldown from a full speed hit

Core Eject

This works perfectly. Though it could use a tracer for hammering projectiles.

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Nailguns

Attractor

The Attractor should shoot silver nails, these have pretty blue tracers and do more damage than the nails from the Overheat and Jumpstart variant.
When magnets despawn, they cause every orbiting projectile to despawn with them, when they should scatter all of them instead.
Magnets break when being hit with the feedbacker, when it should only be from being shot with hitscan.

Overheat

Spawns with only one heat sink (alt) instead of two.
As it gets closer to full heat, the firing speed should slow.

Jumpstart

Doesn't exist, so no feedback.

Sawblade Launchers

Saws should fire in a straight line instead of falling.

Attractor

Ditto as the Attractor Nailgun, but with silver saws.
Additionally, lacks a cooldown, should be 0.25 seconds between each shot.

Overheat

Lacks any indicators on heat level or alt. fire cooldown.
Overheated Saws should ricochet in a straight line.

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Railcannons

Cooldown should be 15 seconds.
Cooldowns should be linked between variants (though if that's not possible due to limitations from being separate weapons, it's fine).
Deploy speed should be instant.

Electric

Lacks piercing.

Malicious

Works perfectly.

Screwdriver

Doesn't exist so no feedback.

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Rocket Launchers

When rockets collide with some objects, instead of exploding they spin out of control and make me laugh.
Deploy speed should be about twice as fast as the Shotguns.
Rockets seem to fire too high above the player, this makes it a bit tougher to rocket jump.
Firing cooldown should be 1 second.

Freezeframe

Alternate fire seems to trigger the cooldown, causing a delay in firing.

S.R.S

Cannonball has no cooldown, should be 8 seconds.
Cannonball should fire at an arc instead of a straight line, however once parried then they should go straight.
Cannonballs explodes when hit with the whiplash, when they should be reeled to you.
Cannonball hitbox seems inconsistent, most noticeable when trying to dunk.

Firestarter

Doesn't exist so no feedback.

That took a lot a lot of writing, can't wait to write some more when I write out the bugs I found in the bugs forum. There may be problems with grammar and the like as I didn't want to proof read all of that too many times, so if you need clarification for anything just ask me. I will also try to keep this updated with the mod.