A great, if near best, weapon in this game. Only true weapon, and only automatic one in this game. If used correctly, you could blow through the entire game on this weapon alone, as it's ammo is plentiful and it's fire is highly damaging.
Primary Fire - High accuracy, high rate of fire, high damage. It just doesn't get much better than this. You can take out a Necromorph with only a few well placed shots. Aim carefully, master this mode of fire, and you'll have no problem at all with this game.
Alt Fire - Not all THAT useful unless you have Necromorphs coming at you from all angles. Your character will duck down and have the gun spray bullets in all directions. It'll get you out of tight spots, but wastes ammo rather quick in the long run. Also, it only really works on tall enemies that actually have legs. Use only if needed.
For as much ammo as it uses, this is probably the most powerful and practical weapon in the entire game. One single shot can take out multiple enemies, and the ammo for it is well beyond plentiful. Only real downside is that it's a very short range weapon that could take some time to master. Buy it, and use it. Use it whenever you know there's a load of enemies around.
Primary Fire - Fires a spinning saw blade held a few feet in front of the character by a gravity tether. Spins for over 10 seconds and can devastate enemies no matter what type they are. Will do a lot of damage for roughly no ammo at all.
Alt Fire - Fires a single saw blade off in one direction and can cut through multiple enemies. Will take one ammo, and can't do all that much damage to enemies in the long run. Use only if there's not much other choice.
Really the only free weapon in this game, and the first one you obtain. Is about mid range on the practicality scale and can be used to some quite devastating results if mastered. It's mainly a short to mid rage weapon, and can be used to get out of some tight spots. Ammo is somewhat plentiful throughout the game, and if you don't feel like buying other weapons, it's a must use.
Primary Fire - Fires a single plasma cutter round out that has little to no trouble cutting through flesh and bone. If aimed right, it can take down an enemy in 2 to 3 shots. Use it to your advantage.
Alt Fire - Changes the fire blade from vertical to horizontal. Not damage effecting at all, just helpful to the primary fire.
Necromorphs have a bad tendency to lay around and wait until you're close to them before leaping up and sinking their claws into you. If you happen to come across one that looks relatively intact, and you're not sure if it's still alive or not, use your abilities. The Kinesis Module does a world of help if used correctly. Simply aim it at the enemy to test it. If the Kinesis Module has no effect on the enemy, then it's still alive. At that point, feel free to pump it full of as many rounds of ammo as you want.
Never let the background music leave your mind, as it could be one of the biggest helps to you in this game that there are. If it's anything above subtle, then there's most likely an enemy near that should be avoided or killed. Only when the music dies down can you know that you're momentarily safe.
For the newcomers to this game, there's one thing that will probably help you out the most if you do it. Shoot the glowing yellow spots. Bosses, common enemies, whatever. If it's yellow and glows, that means it's perfectly fine for you to wail away on from a distance with your weapons. Shoot away, but never be close to one with they take too much, as they are explosive most of the time. Weakness of all bosses.
Probably the only times you'll ever be safe throughout this game are the times when there's a store near, or a bench. Enemies will rarely, if ever come near you when you're within range of one of those devices. Just a safe thought so you can finally have a moment to relax should you need it. There is, however, one exception. Mining Deck, near where you have to run around a massive round chunk of rock to place a device on the outside. There is a bench in that area that will activate a Necromorph if touched. Be careful.
Always keep in mind that it's a needed to always have a Power Node on you. Never use them all on the Benches or sell them all should you choose they're not needed. Scattered throughout the game are certain rooms that can only be accessed if you give up a Power Node to open the door. These rooms generally contain a wealth of ammo, or schematics that could produce helpful items. Unlock ever one of these rooms that you can. They're more important than the nodes themselves, especially on the harder difficulties.
Though it may not happen all that much, if you ever are thrown into a corner with enemies all around you, go crazy. Don't bother with precision weapons such as the pulse rifle or plasma cutter. Either swing your way out, or use the Force Gun to throw them all a ways back. As soon as they're all off, run. Run far away to where you can shoot at your enemies, and use those precision weapons again.
Chose only one weapon to use throughout the game, your best bet is the Pulse Rifle. You will pick up many items in each chapter of the game the game, as well as schematics which allow you to purchase them from the store.
The list of items you can pick up as well as buying from the store are as follows,
Plasma Engery Line Racks Pulse Rounds (You Will Not Sell These) Flame Fuel Force Engergy Ripper Blades Contact Energy Small Med Pack Medium Med Pack Large Med Pack Small Air Can Medium Air Can Stasis Pack Power Nodes (You Will Not Sell These)
You will not get any money for finding Schematics, they will only give you the ability to purchase a certain item from the store.
To upgrade your Weapon of Choice, Rig, Kinesis Module, Stasis Module, sell every item you do not need, this sounds like an obvious solution, but as you only have one weapon, you have alot of ammo for six other weapons to sell, as well as various stasis packs, air cans and med packs which you do not need at present. This will give you a fair bit of money, which will enable you to buy Power Nodes (10,000 each) to upgrade your equipment. Keep in mind you sell items to the store for half the price you buy them for.
If you use this technique properly then you will only be buying Power Nodes, ammo for your chosen gun, and the odd med pack, stasis pack and air can when needed.