Your first and most basic weapon. You pick it up in Unforeseen Consequences. They are useful for opening crates. They can also be used to kill head crabs, barnacles and if you want to take a risk, zombies.

Found in Unforeseen Consequences this weapon is useful all through the game. It can take out a large number of different enemies with few shots. There are 17 bullets per clip and you can hold up to 250, this uses the same ammo as the MI5.

This is a very powerful weapon. It can be used to take out more difficult enemies quickly. Be careful though as you can only hold up to 36 bullets with 6 per shell. You first find it at the end of Blast Pit.

This weapon is one of the most useful against the marines, it has a fast fire rate and large shells, 50 bullets in each. You can carry up to 250 bullets. It also has a secondary fire of small grenades, you can hold up to 10 of these. You first get this weapon in 'We've Got Hostiles'.

This weapon is effective close up but its slow reload time makes in impractical when fighting multiple enemies. There are 8 shells in a clip and you can hold up to 125 shells. First found in Office Complex.

Shoots darts to kill an enemy, can be used underwater unlike most weapons. Is first found in Apprehension and can hold up to 50 darts with 5 per clip.

This weapon is very effective against tanks, helicopters and bosses. You will pick it up near the end of surface tension. You can hold up to 6 rockets (5 officially but you can have one loaded).

This weapon shoots energy bursts and can be charged up using the alternate fire button. It takes out alien grunts very quickly. You first find it in Questionable Ethics. You can get up to 100 ammo.

This weapon is very similar to the gauss gun and uses the same ammo but has a more constant stream of energy. You find this weapon in Lambda Core.

This has 8 homing beasts which regenerate after you fire them out. They are useful for getting enemies when they are just out of sight. This was one of my favourite weapons. You find it in surface tension.

These are useful when fighting tentacles and for scaring marines. If you hold them before you throw (holding down fire key) then they will go off more quickly. Remember looking higher makes the grenade go further. You first find them in unforeseen consequences and you can hold up to 10.

These are remote controlled, throw them then click again to fire. Can be used to take out a number of enemies. You can hold up to 5 and they are first found in on a rail.

These can be placed on any surface, they will produce a blue beam which will cause them to explode when broken. You can hold up to 5 and they are first found in power up.

First found in Questionable Ethics. These little beasts will attack the nearest creature and then explode, beware if there is nothing else to attack they will head for you.