It appears that the rocket launcher, at least in the Public Beta, has lost its ability to lock on to vehicles, and has returned to its Halo 1 configuration in that respect.

What does have the ability to lock is the new Missile Pod, another heavy weapon.

Like the portable turret, you can't zoom, drive or ride in vehicles, run, or crouch while wielding it.

NOTE: Information from the beta version subject to change!

In addition to deployable equipment, Halo 3 seems to have a new category of "heavy weapons" that have special characteristics.

One is a variation on the fixed turret-mounted machine guns we're familiar with from Halo 2. They can be used from a fixed position. However, pressing the B key removes the gun from its turret so you can carry it with you. In this configuration it has limited ammunition, and also enforces other limitations on you.

A new addition for Halo 3, the Spike Grenade works a bit differently than frag or plasma grenades.

Like a plasma grenade, it will stick to targets. Unlike a plasma grenade, it will also stick to walls, floors, and ceilings. Also unlike a plasma grenade or a frag grenade, it unleashes damage in a conical pattern away from the surface to which it sticks.

Full lowdown on this weapon can be had from Bungie.net:

Brute Grenade Top Story

With the release of Halo 3, Bungie fans will be looking at new vehicles, new weapons, new maps, and new opponents. To kick off the promotional campaign for the game, the website Halo3.com launched late last month, with some preliminary information on Halo 3's characters, weapons, and vehicles, as well as a summary of the story to date.

A combination of ceremonial elegance and practical power, the twin-bladed Energy Sword can be used as a slashing melee weapon, or in correct fighting technique, the wielder waits until the opponent reaches a perfect distance and lunges forward in a ferocious attack.

NOTE: So it looks like the melee lunge is still in, which means that fall damage is out. No word on how the weapon actally works, though. In Halo 2, the weapon was limited in campaign mode like all Covenant energy weapons, but in multiplayer it was unlimited. Will that remain? Time will tell.

Holding 40 spikes per magazine, this vicious and dangerous rifle is favored by Brutes and in fact, is based on their native pre-Covenant technology. Old as its technology is, the rapid firing razor-sharp projectiles can tear through armor and flesh with ease.

Detailed specifications are available from this Bungie.net feature story:

The Spiker

A hand carried particle beam acceleration weapon. Its range is basically only limited by its five or 10x zoom scope, and atmospheric conditions. The rifle carries a power cell good for up to 18 bursts and charges very rapidly for a weapon of this type.