Half-Life 2's entire collection of weapons won't be known until the game is actually out, but here's what's confirmed thus far:

Crowbar

It wouldn't be Half-Life without the crowbar! In Half-Life 2, the crowbar's alternate fire flings a combination of hard-boiled eggs and lasers at your enemies. Just kidding.

Pistol

It's a pistol. It probably shoots bullets. More accurately, it looks to be a H&K USP Match, the same gun carried by Angelina Jolie in the Tomb Raider movie.

Shotgun

The shotgun is also returning. It probably shoots shotgun shells which cause damage if you stand in front of them while they're being shot at your head. It seems to be modeled after the Italian SPAS-12.

Machine Gun

There's a machine gun, but Valve says it's not an MP5 and a lot of people seem to think it's an MP7 or a H&K PDW. Just keep in mind that since Half-Life 2 takes place in the future, it could be something else. There are screenshots that show various enemies carrying what appear to be MP5k's, though.

M-29

This gun appears to be based on the M-29 OICW (Objective Individual Combat Weapon). It could just be a coincidence or some kind of futuristic variant or something, though.

Rocket Propelled Grenade Launcher

The RPG from the original Half-Life is also returning, although the targeting laser now seems to be a little more advanced.

Alien Spore Globe

We have no idea what the final name of this thing will be, but basically, they're little alien globe things that you throw at enemies or objects you want to attack. The spore emits a special pheromone that attracts Ant Lion aliens, and those aliens swarm towards the scent and kill anything in the vicinity of where you threw the globe.

Gauss Gun

The Gauss Gun\Tau Cannon from Half-Life also appears to be making a comeback, in the gameplay video it's mounted on a vehicle, but we're guessing you'll be able to carry one around too.

"The Manipulator"

We don't know exactly what it'll be called in the final game, but the Manipulator is a weapon that allows you to grab various objects with a gravity beam. For example, you can shoot the beam at a chair, lock onto it, and then swing the chair around in the air. Alternate fire lets you shoot the object you're controlling. For example, you could pull the sign off a building with the beam, then use alternate fire to fling the sign towards an enemy to crush them. According to Gabe Newell, "The manipulator 'opens' when you can pick something up that you are pointing it at. There is a weight limit. Most everything can be picked up."

Grenade Launcher

We're pretty sure this is a grenade launcher. You can see it in action in the Tunnels video. Some people insist that this is a flare gun, and while the Combine are shown shooting a flare into the air in one video, it's unclear at this time whether the flare gun will be a usable weapon in the final game.

Fragmentation Grenade(s)

Youll have at least one type of grenade at your disposal.