I think the ripper is by far the best gun in the game. Only because one ripper saw can kill as many necromorphs as there are coming at you. Even without upgrades it kills everything very quickly, and isn't too expensive to reload.
I really can't believe how many people love the plasma cutter. Near the end of the game it becomes virtually useless. All of the necro's are black and it takes like 3 shots just to blow off one limb. I had it upgraded to the max and couldn't have been more displeased with it, it became a huge ammo chugger. I ended up spending so much money just buying ammo for that piece of shit that the first time i got to the last boss, i literally had not enough ammo to beat it. I went back a few chapters and switched it out for the ripper, and the game became 10X easier. I could actually get through the last chapter and take my time, instead of booking it most of the way through.
Where the ripper really shines is when they send a lot of the little baby thingies at you, or just hordes of enemies. You just keep one saw spinning in front of you, and they literally shred themselves to death on it. If there's a big enough horde coming, one saw can kill up to 10 enemies (i think that's the most I've done). Then with that one saw, you've earned probably at least quadruple the ammo you've used. Best gun in the game next to the line gun.
As for the other guns, it doesn't really matter. Once you have the line gun and ripper fully upgraded that's all you need. Everything else is just for fun. Though I did really enjoy the contact gun, and used it mainly for selling the ammo I found for it (most expensive ammo in the game), and I used it as a boss killer (it took 3 shots to kill the last boss
). Then I used the force gun for the very rare moments when I would get overwhelmed (literally never happened after I got the ripper), and I used it for stalkers.
About to start playing it on hardcore, and I'm sure it won't be that bad once I get the ripper...... did i mention how much i like the ripper?