This answer is made with the assumption that the goal is to occupy the space station after combat has resolved. If we're not taking the station, then there is no need for combat on board the station. It's much easier to sabotage it or destroy it.
I'm also assuming that, since there's no artificial gravity, we aren't using any other handwavium technology like force fields, repulsors, or anything that is unlikely to be used in the next 100 years.
In space, whether inside or outside, your options are grouped into kinetic slugs (firearms), missiles (rocket propelled grenades), chemical sprays (flamethrowers), or directed energy weapons (lasers).
Railguns, bows and arrows, rifles, handguns, flechettes (dart guns), cannons, shotguns, shuriken, throwing axes, etc., are all examples of kinetic weapons.
The main problem with a kinetic weapon isn't just Newton's second law (every action has an equal and opposite reaction), but the fact that you're usually using your arms in some ways, whether holding a firearm or throwing something.
That's going to set you spinning, because Newton's second law is also works right along side the Law of Conservation of Angular Momentum. If the point that you're launching something from is off-center from your own center of mass, you're going to start rotating.
So, rule number 1 of kinetic weapons in a ship: Unless you've very careful to "fire" from your center of mass (which is a bad idea for other reasons, namely you making yourself a bigger target), you must secure yourself.
That's easy, though. Every manned spaceship since the Mercury capsules have had plenty of handholds and footholds. One of the most common complaints of astronauts aboard the International Space Station is that the tops of their feet get sore, from sticking their feet into these footholds.
The second problem with a kinetic weapon is that you're likely to miss.
Yes, you might poke a hole in the ship's hull and let the vacuum of space inside. Even for a tiny ship like the International Space Station, a small arms bullet hole would take a couple of hours to dangerously depressurize the ship. Plenty of time to close a pressure hatch and don a pressure suit so that you can go make repairs. Just don't make a habit out of missing.
More immediately dangerous, and quite likely to make the ship permanently uninhabitable, is if you rupture the coolant system.
Heat is a HUGE problem in space. Yes, space itself is cold. Space also happens to be one of the best insulators, because you can't conduct or convect heat away; you can only radiate it away.
Every light source emits heat, even low energy LEDs. Every human emits heat. Every pump in the life support system and water reclamation systems emit heat. Everything that creates and uses electricity emits heat. Even the refrigerator creates a net increase in heat.
The best chemical for carrying all of that heat out to the radiators, that keep enclosed spaces cool enough for humans to live and work? Ammonia. Not the heavily diluted stuff in window cleaning solutions, but pure, undiluted, toxically deadly ammonia. That's what the International Space Station uses, as did Mir, Tiangong-1, and SpaceLab. (The US Space Shuttles and USSR Burans used water, but their life support was limited to 2 week missions, maximum.)
Ammonia is fine on Earth in small doses. It evaporates quickly, is lighter than air, and is rarely released in large enough concentrations to cause environmental impacts.
Ammonia is a quick and painful death if you're in a sealed environment, as it will chemically burn your lungs to mush. With no "up" for the ammonia to float away to, it will stay around until a very thorough decontamination is performed. (If the ammonia coolant in the ISS leaks into the living space, plans are to abandon the station and remotely command a controlled deorbit into the Pacific.)
More dangerous than the ammonia, though, is the threat of fire from sparks given off when these kinetic weapons strike something metal. This is less likely, though.
Because of the null gravity, fire burns slow and methodical, and spreads its fuel around before consuming it. The first place that the fire will go is right into the life support system, right to the air intake filters that are full of all sorts of fuel like dead skin cells, crumbs from your lunch, discarded hair, etc... and the filters themselves are unlikely to be flame resistant. Next stop is the CO2 scrubbers, then the O2 outlet nozzles.
The best case scenario in a fire is that your life support system shuts off. Air stops flowing around, which will slow the spread of flame and keep a pocket of oxygen rich air around you. Depending on how big of a room you're in, your most immediate concern will likely be CO2 poisoning (headaches, nausea, disorientation, fatigue, and finally death through toxic buildup) before you'll have to worry about suffocation from lack of oxygen. This will take several hours or even days, so long as the fire is contained and isn't spreading smoke through the entire ship.
But, starting a fire will likely make the station uninhabitable, and will be an undesirable outcome for the attacking party.
Fortunately, little on space ships are flammable, specifically because of how unreasonably dangerous fires are. Accidentally starting a fire from sparks is unlikely. Especially since Apollo 1.
Quick recap of kinetic weapons: You need to brace yourself when using it, it's alright to puncture the hull a few times, but if you hit the wrong thing, everyone loses.
Next up are missiles. The least advanced of these are little more than kinetic slugs that have their propellent attached to the bullet, rather than relying on the propellent being consumed all at once inside the barrel of a gun.
The main advantage is that it doesn't impart much of that "equal and opposite reaction" force on the person who fired it, making it possible for a combattant to fire it without being secured to a bulkhead.
Additionally, it makes it more comfortable to fire larger masses at a target, such as a mass that includes high explosives. A typical use case would be a rocket propelled grenade.
With more mass in your payload, you can also add some limited guidance. Probably not helpful in fighting happening entirely on a ship, which will be at extremely close range, but if there were a drone or other small spaceship taking potshots from space, too far to hit with any real accuracy, you could potentially train a targeting laser on it, letting the missile do the hard work.
As far as explosions on a spaceship, a suitably well built station would survive an internal explosion better than any humans aboard. Spaceships are designed to hold pressure in.
There are some very gruesome facts about explosions and mammals that are best left to the morbidly curious. While many people think that the shrapnel from a grenade is the most dangerous part, the actual most dangerous part is the pressure wave.
Because space stations tend to be very long tubes, the pressure wave doesn't have much chance to spread out and dissipate. Because the diameter of the liveable area of the International Space Station is about 7 feet across, a high explosive grenade will be just as deadly 7 feet away as it is 200 feet away (and that wave will bounce back a few times). You're going to want to close a pressure hatch before using high explosives on the other side. At the very least, it will rupture everyone's eardrums.
And even then, even though the station is likely to fare better than humans in case of an explosion, the pressure wave will seek out the weakest points, and will probably find one. It will probably crack a weld and introduce a slow leak, making it necessary to wear pressure suits within a couple of hours.
First, a pedantic note: These impart momentum under Newton's second law, just like kinetic weapons. It's like a garden hose: there's a noticeable force when you have it on full blast.
Anyways, regardless of whether you can reliably aim a stream of liquid or gasses, chemical sprays are just a Bad Idea(tm). You'll want to live in the station. Spaceships have closed life support loops, and air moves very slowly. With no "up," toxic chemicals linger in the air, neither rising nor settling.
If you think about igniting that chemical for some reason, such as if you're using a flamethrower, it would be much easier to destroy the station outright, since nobody will be taking control of it in the near future.
Lasers. More pew-pew.
Lasers are probably not viable. At least not if you want your sci-fi to be faithful to basic laws of physics.
At least lasers follow basic laws of physics, though. Lightning guns and plasma bolts are right out. They're not sci-fi, they're fantasy.
I mentioned above that heat is a problem on spaceships. There is no convection or conduction, only radiating the heat.
The general rule of thumb for a laser is that it takes as much heat to make a beam as that beam will deliver to the target.
In order to ablate away enough flesh to seriously wound a person in a blast that's short enough in duration that the person won't just hide away, you need a 4 megawatt laser. That's not a portable laser simply due to the energy requirements. It's either attached to a generator (larger than any camping generators you can find), or attached to a bank of batteries that take up a significant portion of a large room. Best case scenario, you have a monster sized power cord plugged into the station's power.
With that laser, over the course of a second, you deliver 1000 kcal to your target. You also deliver 1000 kcal directly to the station's radiators. Keeping in mind that the ship is a closed system, and all heat has to eventually be radiated away, the 1000 kcal that you delivered to your target also has to make its way to the radiators. Every shot costs the radiators about 2000 kcal of extra work. If the space station is a battle station, then this is fine; the radiators will be designed to handle a few batteries of gigawatt lasers. If it's a civilian space station? Your next step after taking the station will be to replace the radiators, or you'll all quickly roast.
Null-G Combat Tactics
I'm including this section because tactics inform weapon choices.
Good tactics in any combat situation with firearms is to present as little cross section to the enemy as possible. This means using cover and concealment, using covering fire from squadmates when you need to move, so that the enemy is less likely to poke their heads up and take a shot at you, etc.
In null-G, you have an extra advantage: You almost never have to present your full torso to your enemy. Put some extra shielding on your feet and make that the only thing you present to your enemy. Something like 4" thick bulletproof clear acrylic sheets with a small hole that you can poke the barrel of your rifle through. You'll lose some accuracy, but your cover comes with you. (Or, if you care more about accuracy than protection and mobility, you can adopt more of a "Superman" pose than an "Enemy's Gate is Down" pose by putting the acrylic sheet above/in front of you, so that you can swivel your firearm faster.)
And finally, the big question:
Do you want to intentionally evacuate the air in the station during the attack?
All weapons will still work. Firearms since muskets have been able to work in a vacuum. I know, "But there's no oxygen in the vacuum of space!" ... Well, there's plenty of oxygen inside of every explosive that humans make. (Pedantic note: when it's in an explosive, it's called an oxidizer, and is often not found as the gaseous oxygen that we breath.) All of the weapons that I listed absolutely work in space.
There are a couple of differences; explosives don't create shock waves in a vacuum, but they DO fill up an unpressurized space with smoke very quickly.
There are tactical advantages and disadvantages to intentionally letting the vacuum inside. Anyone caught unaware is having a very bad day. Depending on how quickly you can let the air out, people may have as little as 10 seconds to react. That can quickly reduce the strength of opposing forces that you have to deal with.
A disadvantage, though, is that every wound becomes debilitating.
Additionally, your mobility is severely limited, and your vision can be instantly obstructed. Fighting slows dramatically, since just dashing across a corridor becomes an incredibly risky action.