Hey, wait a second--I'm someone!
1. Your starting gun, the Clutch Buster, is great for single enemies or small groups of lower-level enemies--the primary fire stunlocks an enemy reliably, and your punches are a solid option in close quarters. One punch is enough to down most zombies, two will take out imps and chaingunners, and three punches will K.O. a pinky--and you can punch as fast as you hit the button! Anything larger than a pinky is best dealt with using guns, though.
1c. The Spark Injector gains ammo when you hit with its normal swings, and uses ammo for its charge slice and altfire. Both the charge slice and the tazer use 10 points of ammo each time, so every ten hits gives you another shot. It does about as much damage as your regular punch with the normal swing--it actually takes four hits to kill a pinky with it, instead of the three-hit combo you'd normally do. But where it really shines is against larger enemies--stun one, then keep swinging to get your ammo back. The charge slice has an AoE, but it also does decent damage against single targets. Overall, it's a decent alternative to the Clutch Buster, if you've got other weapons you can use at distance.
2. The Jet Divider is a solid option for groups of enemies or things with large hitboxes, but it does suffer against single targets. Primary fire will keep going forever, but it does spread out over time, and the individual flames waggle unpredictably. If you can land it right, you can take out two imps with one shot, and anything smaller is even easier to deal with. Altfire's flames rip through targets, so they're ideal for clusters of enemies. If you're up against one big guy and you haven't got any bigger guns, you can use the JD, but your hand cannon is honestly a better choice for this, because it stunlocks more reliably.
3. The Nitro Wheel is the ultimate approach weapon--it blocks projectiles! Primary fire ignites the wheel. Leaving it up costs nothing, but if you switch away, you'll lose the wheel. Holding primary fire while the wheel's up will boost you forward, and damages enemies around you--it's good for running through crowds when you don't have the Speed Booster yet. Altfire, on the other hand, is where it's at--you'll flash-ignite the wheel, causing it to explode outward. The damage on this is just enough to kill Hellknights in one shot sometimes, and it has a larger radius than you'd think! The main problem is that altfire uses up five ammo, on top of the first point of ammo you used to create the wheel. Also, archvile fire bypasses the wheel's protection. Use the Nitro Wheel when you need to close the gap with Arachnotrons, Hell royalty, or any other monster that likes to toss meaty projectiles at you.
4. The Volt Driver is a good singletarget weapon, and cuts through crowds almost as good as the Jet Divider's altfire. However, its primary fire has a limit--the sparks fade out after a bit. The altfire is better--it has unlimited range and does splash damage, but uses 20 ammo at a time. That said, you won't hurt yourself with the Volt Driver's blast, so feel free to use it in close quarters. You can't actually use the altfire until it's fully charged, so I like to dip in and out of cover when using it.
5. The Heavy Cylinder is a long-range bread and butter weapon. Like the vanilla RL, it mauls crowds and is easy to spam. Altfire launches the rockets as grenades instead, which is great for dealing with archviles--press the button again to detonate. Try to time it so they go off right as they hit the enemy--they do bounce off. Amusingly enough, the altfire grenades will actually kill zombies on impact, without exploding! Bonk! Use grenades for indirect combat, and the rockets to deal with things that are far away.
6. The Crush Piston is maybe the only gun in the mod that's genuinely useful for almost anything. Against single targets, you no longer have to aim. Against groups, your altfire will clean up--and by the way, the altfire missiles will find new targets if the old target dies before they get there. And the altfire missiles have noclip. Revenants hate this one simple trick...
7. All Brake's primary fire is a timestop. Press the button again when you've finished doing your best DIO impression. Altfire is the pinball effect, but it costs a lot of ammo.
8. Side Passenger doesn't use your Clutch Buster ammo. It'll always fire at the exact same spot you're firing at, but from a position roughly a second behind you. If you want to, you can hit altfire to make the Side Passenger act like a turret--while in this mode, it'll fire automatically, but it'll still go away if you deselect. It stuns even more reliably than the Clutch Buster, and does more damage than you'd think.
R. Hitting the Reload button charges forward, knocking enemies back! It recharges over time, so don't be afraid to use it. You'll hear a vroom when it's ready.
Z. Hitting the Zoom button activates Blueshift, which makes you go even faster beyond. I can't tell if it does anything else, yet. [EDIT] It makes everything faster. Including guns.[/EDIT] It recharges over time, too--but it takes longer to recharge. You'll hear a countdown beep (3...2...1...go!) when it's ready to go again.
H. Honking alerts nearby enemies. Makes them jump a couple feet in the air, too!
A. Armor absorbs 100% of damage and prevents knockback, but it'll be gone fast. You'll hear a different hurt sound when the damage is absorbed by armor, so you'll know when you're out without looking.