Even though I feel like a stick in the mud, I've stuck to something similar to my DS1 arsenal
Plasma Cutter for just about everything that wasn't the 3 tentacled thing, a pack, or those flood looking things that spawn from the pregnants.
Line Gun - I really don't know if I need to keep this thing around, I used it in the original because it was literally the only weapon I knew of that could deal with the babies(I don't know if that's the name, but the 3 pronged necros that spit at you) without wasting tons of ammo. So far it's been a pretty shitty choice, as I've seen maybe 4 of those things in 7 chapters. It's actually not terrible against the slashers/pukers/spitters, it's just really slow to aim and fire, so it's kind of a bad choice to be walking around with it as your primary weapon.
Pulse Rifle - This sort of served as my last resort weapon in DS1, mostly because I never really sunk too many nodes, but it's pretty awesome in DS2. Been using it vs the pack, the flood, as my primary when I run low on plasma cutter.
Cutter - I never really used a 4th weapon in DS1, but holy shit is this thing amazing. Absolutely  my go-to when shit just gets insane.
 
I'm kind of curious since playing on Survivalist doesn't really leave you with much room to experiment with all the weapons.

I played the majority of the game on normal with the Plasma Cutter and Pulse Rifle.  I tried a few various weapons (the shotgun thing and the contact gun) but ending up selling them.  I also had a line gun for about the last third. 
 
If I have one complaint about Dead Space, it's that the weapon choices aren't too good, at least from what I can tell. 

I have one... The Line Gun.

" I have one... The Line Gun. "

" @TomA said:

" I have one... The Line Gun. "

Once you fully upgrade the alt-fire, it might as-well be a nuke. "

last time when I finished third game, I had plasma cutter (max upgrade), pulse rifle (max upgrade), zealot force gun (70% upgrade), seeker rifle (60% upgrade). especially, zealot force gun really kicks 90% necromorphs by one shot. sometime when I will play again, I will upgrade it for 100%. seek rifle is very useful. literally, one shot one kill (when you upgrade more than 30%). when you aim it, it actually zoom in so that you can easily point to necro for killing instantly. anyway,  I will attempt to upgrade all of weapons for full next time.   
 
PS) try force gun. I bet that you won't disappoint. it's very powerful weapon. see yourself.  but it doesn't work well for big necros like tripod, jellyfish thing (shoots red ball in space), guardian (throwing grenade is instant kill).  

I tend to roll with Force Gun, Ripper and Line Gun.  I try and get any as many kills as possible by using kinesis to spear Necromorphs to things, that never gets old!

Plasma Cutter. 
 
Line Gun. 
 
All you need.

I had plasma cutter, pulse rifle, line gun and contact beam. I mostly used the pulse rifle and plasma cutter, I almost never used the line gun except to use it's alt against the little things that crawl on you I would use stasis then plant one of those mines and boom, I probably should of changed the line gun for the detonator cause of those stalkers man those were annoying, I also tried the seeker rifle but didn't think it was pretty good, the contact beam is amazing one shot straight to the body of a normal necromorph and it explodes so satisfying every time also with upgrades it's the strongest weapon in my opinion. I was hoping to see that sword thing from the first animation movie that thing looked cool.

Plasma cutter, force gun and line gun for tripods.

Plasma Cutter, Pulse Rifle, Line Gun, and Javelin Gun. Used those through my first playthough, using all the other guns here in my second.

I only used the Plasma Cutter and the Pulse Rifle on my first playthrough.

-Plasma Cutter 
-Line Gun 
-Pulse Rifle 
-Contact Beam or Seeker Rifle

I'm on round two on normal (playing through to nab some missed achievements and upgrade a bunch of stuff for zealot) - and I've been running with the Plasma Cutter, Line Gun, Pulse Rifle, and Detonator. 
 
Serioiusly. If you have not played with the Detonator - give it a try. It's friggin' awesome, or at least when it's fully upgraded.

Zealot mode I switched around to get achievements.
Hardcore mode I only used the Plasma Cutter.
Casual NG+, HAND GUN PEW PEW PEW BANG! BANG!

For hardcore mode I rolled with contact beam, plasma cutter, seeker rifle and force gun. Contact and force to give me some breathing room, the other two for precision killing.

I went through the whole game with nothing but the Plasma Cutter and Line Gun. I'll pick up the others on my second playthrough purely for achievements.

Fuck the line gun and the contact beam and the seeker rifle.
 
Javelin Gun is the bees knees.
This baby when fully upgraded does 100 damamge thats the same as the Contact Beam but is much more manuverable and fires/reloads faster.
It one shots all standart necromorphs to the body, (nailing them to a wall is a bonus)
Elite necros need a second shot or simply alt fire to make your stake electrocute and explode.
Explosion of alt fire has the bonus of killing all nearby necromorphs too. There is nothing quite like taking out 2 elite necromorphs with one shot and a secondary folow up.
The ammo for Javelin Gun is DIRT CHEAP - 400 per 2 shots (360 with suit) 
This is an incredibly cost efficient weapon.
I literaly just ran through the last chapter non stop taking out dudes left and right never bothering to even stop, just reloading on the fly.

plasma cutter, line gun, pulse rifle, force gun

I used the Plasma Cutter and that's it, never even bought any of the others. I thought there might be another One Gun achievement, but no. If/when I play it again I'll check out the rest of them.

Plasma Cutter, Plasma Cutter (the one you get for playing the first game), Ripper, Line Gun. That got me though on zealot without much trouble. 

First playthrough had me rockin' the Pulse Rifle as standard, unremarkable but still reliable main weapon. There's the Contact Beam that helped greatly for those infuriating dinosaur like necromorphs that charge at you, as well its alt fire was fantastic for crowd control. Specially since Isaac becomes invincible soon as he begins the animation for it, as well. 
I had me the Ripper for general crowd control and getting through corners, and finally the Line Gun for when all fails and need to kill these bastards quick.  

My absolute favorite is The Ripper.  Nothing can withstand the might of The Ripper.

Plasma Cutter, Line Gun, Javelin Gun, and Flamethrower. Probably going to replace the flamethrower once I get the schematic for the Force Gun. 

Plasma Cutter - Fully upgraded this gun alone could probably see you through the entire game. 
 
Pulse Rifle - A good all around assault rifle with a good AOE grenade launcher for crowd control. 
 
Contact Beam - Currently my favourite weapon. I highly recommend that you fully upgrade this to get the stasis mod, it kills any necromorph that stands next to you and knocks others down as well as putting them in stasis. This gives you enough time to fire a contact beam round into them. Awesome for crowd control. 
 
That's all I used for my first two playthroughs. On my third playthrough (hardcore), I will probably only use the plasma cutter and line gun so I can devote power nodes to my RIG. 

Zealot Force Gun- This thing tears everything apart 
Contact Beam 
Refurbished Plasma Cutter 
Line Gun

" I used the Plasma Cutter and that's it, never even bought any of the others. I thought there might be another One Gun achievement, but no. If/when I play it again I'll check out the rest of them. "

I only used the plasma cutter.

I used the Plasma Cutter, The Javalin, Contact Beam, and Seeker Rifle.  
 
I used the line gun a lot in the first few chapters, but switched it out for the seeker Rifle because I used it so much in the first game. I tried to use the force gun for awhile, since i like it in the first game, but i just couldnt find a good use for it.  
 
I am already looking forward to playing it again to try out different guns, i think its time i gave the pulse rifle a chance, i never gave it the time of day in the first or second game. 

Pulse Rifle and Force Gun. The Force Gun is great for all close combat encounters, while the Pulse rifle takes care of medium and long range.

plasma cutter. that is all. 

Plasma Cutter, Pulse Rifle and Force Gun all max upgrades and I've been switching out the fourth to find my favorite sniper... the Seeker rifle and Contact Beam are both fun and I think im going to bring back the old Javelin next.

Hand Cannon now that I've unlocked it. Best gun ever.

plasma cutter, blank, blank and blank

Plasma cutter. There are more guns?

I'm liking the 4 the OP uses. I just tried to talk myself into dumping the pulse, but I can't do it, and I want to experience it's gernade function more. The cutter rocks. The line gun is  both powerful and wide area, and the plasma cutter is a good primary weapon. In DS 1 the pulse was almost required for the big worm things, here not so much, though I have only fought simular but not same critters here. 
 
In DS 1 ,I used that big gun in the end. It worked well, but that was the appropiatte time for it. 
 
It's hard to be imaginative beyond this set-up, but I do want to try. I can always sell them back...

Plasma Cutter- Good, basic weapon that can be used in almost any encounter. 

Force Gun- Pretty much the best weapon in the game.  Want to simultaneously blow off all the limbs of an approaching necromorph?  Use your force gun.  Is your health low and you don't want to let that slasher get too close?  Use the secondary fire for what is essentially a mini-contact beam.  It's a fantastic panic weapon!  If I'm backed into a corner I just unload my force gun and my necromorph problem is gone.  Hate those pain-in-the-ass mini-necromorphs that come in groups and are difficult to take out with your plasma cutter?  One shot from your force gun from medium distance and they disappear real quick!  Seriously people, you need to be using this gun.  And if you call within the next 20 minutes, I'll throw in an extra ten rounds of force energy at absolutely no cost to you!
 
Contact Beam- If you're facing an enemy with a lot of health, the contact beam is one of your best choices.  Use stasis on a brute and you can cut his arm off in one shot.  The secondary fire is great when you're surrounded and need a bit of breathing room.   Once stasis is added to the secondary fire, the gun can be a life-saver.
 
I really only use these three guns, but I'll give an honorable mention to the Detonator.  Nothing is better for dealing with stalkers, as long as you know they're coming ahead of time.  Before they appear, just lay a ton of mines down and the stalkers will run into them and kill themselves for you.

I went with the Plasma Cutter and Line Gun until I reached the bit in the Church where the Pulse Rifle unlocks, then I sold the Plasma Cutter. I pretty much just used those, though for a while in the midgame I had the flamer I decided it was pretty crap fairly quickly and sold it back off again.
 
I played on Zealot, but I have to admit that M+KB make it a lot easier.
 
Edit: Oh and if I go for a new game+ I'm definitely using the Javellin gun, I was wary of it being kind of crap but damn does the ammo for it look cheap. I'll probably stick with the plasma cutter as well because I really did miss being able to switch the angle of my blasts.
 
Also, did anyone really shoot the swarming children necros? I would shoot the first one, and then use its corpse to kill another etc. They were like paper.

Plasma Cutter, pulse rifle, ripper, and flame thrower : It was the exact same setup I had for the first Dead Space and it served me well.  Except the flame thrower, it stinks for killing anything bigger than those swarms but it looks cool doing it.

The old style line gun and the machine gun thingo as a backup are all you need.

I've only got 2: the Plasma Cutter and Pulse Rifle.  Easier to manage with upgrades and ammo.  I did the same for DS1. 
 
When I've beaten all the modes, as I just did Hardcore Mode tonight, it's fun to mess around with the others.  The fully upgraded Javeline Gun is very enjoyable and satisfying.

Handcannon's all you need.

" Plasma Cutter.  Line Gun.  All you need. "

Plasma Cutter, Line Gun, Contact Beam and whatever else

The ripper is all you need.  It slices, it dices, it grinds up anything and everything.  Easily the best weapon in this game and the last.
 
I keep the pulse rifle handy just for things that explode when you kill them.