As the war between the Inner Sphere and The Clans intensified, the need for new and innovative weapons caused an explosion (excuse the pun) in the variety of weapons availible, especially in the missile category.

In addition to the normal conventional and streak missile weapons listed by WWWWolf, the Inner Sphere has availible to it:

Acid Warheads: These missiles are equipped with acidic warheads that do extra damage to certain types of armor, including Ferro-Fibrous.

Follow the leader: Acting like a flock of lemmings, these missiles have a higher percentage of a chance to hit, however the added technology requires more space than standard missiles.

Tandem Charge: Similar to bunker busters, these missles have a delayed charge that is intended to cause damage to the internal structure of the target, with the hopes of causing critical hits to vital systems. The drawback is that they only do half as much damage if the target has no armor to pierce.

One Shot Launchers: For those who want the capability of launching missles without the danger of carrying the large amounts of explodable ammunition to go with it, this single shot launcher is recommended. The only ammunition it holds is the missles already primed to fire.

Thunder Rounds: Not to be confused with a Thunderbolt Launcher, these missiles function as scatterable minefields. While not a direct-combat weapon of choice, given enough time before combat, these are the perfect booby trap weapons, as the enemy will have difficulty noticing mines in the middle of combat before it is too late.

Thunderbolt Launcher*: Rather than firing many small missiles which hit with dissapointing accuracy, the concept behind the thunder missile is to pack the damage capacity of several missiles into one. Picture a Scud launched from a Battlemech.

Dead-Fire Missiles: These missles have been stripped of their guidance systems to reduce weight. While just as deadly as their normal counterparts, fewer of them actually hit their intended target.

Narc Missile Beacon: Fired from a special launcher, this is a beacon for conventional missiles that have been armed with narc tracking warheads. The idea is that a light scout mech 'tags' enemy mechs with the missile beacon which allows other mechs a better chance to hit the target.

Shoot and Sit: An alternative ordinance for the Narc launcher is the Shoot and Sit missile. Using the same technology as the Narc, these missiles 'latch on' to enemy mechs. The difference is that the shoot and sit warheads can be denotated at any time by a remote detonation signal.

There are several others as well, but these are all that I could describe from memory based on a list I found on the net. It has been several years since I've played and so may have made a few minor mistakes above - feel free to msg me corrections.